Research will be limited to:
- Standard: ASTM
- Process: Corrosion Fatigue Testing
- Subject: Specimen Preparation
- Subject: Environmental Exposure

Strategy: I will identify the primary ASTM standards governing the preparation of specimens for corrosion fatigue testing and the specific protocols for environmental exposure during these tests. The search will focus on standards that bridge the gap between fatigue testing (E466/E606) and corrosion testing (G-series), specifically looking for E1437 or related guides for environmentally assisted cracking.
Queries:
- ASTM standard corrosion fatigue specimen preparation surface finish
- ASTM E1437 corrosion fatigue testing metals
- ASTM G44 G31 environmental exposure fatigue testing
- ASTM E466 specimen preparation corrosion environment
- ASTM standard environmental cell design corrosion fatigue

Executing 5 concurrent searches:
- ASTM standard corrosion fatigue specimen preparation surface finish
- ASTM E1437 corrosion fatigue testing metals
- ASTM G44 G31 environmental exposure fatigue testing
- ASTM E466 specimen preparation corrosion environment
- ASTM standard environmental cell design corrosion fatigue

Found 5 papers. Key excerpts:

Corrosion fatigue and damage tolerance in the nickel-based superalloy RR1000 subjected to SO2 environments — Martin Bache et al., 2022

1 INTRODUCTION

     Nickel-based superalloys are a natural choice for engineering applications that demand structural integrity at temperatures exceeding 600°C.1 Despite their relatively high density, a resistance to oxidation and corrosion coupled with high static strength, creep tolerance, and fatigue endurance has sustained long-term employment in the high-pressure compressor and turbine sections of gas turbine aeroengines. To enable gains in fuel efficiency and to reduce emissions, the operating temperatures experienced by key components within the gas turbine are progressively increasing, to the point where hitherto benign combinations of temperature and gaseous environment may now introduce the potential for additional damage mechanisms.

     Type II hot corrosion, resulting from the chemical reaction between the substrate alloy and molten eutectic salt deposits and usually prevalent across the temperature range 600–750°C, is one such mechanism that must now be considered.2 Following dissolution and subsequent penetration of the protective oxide scale, itself composed of two distinct layers enriched in nickel/cobalt and titanium/chromium/aluminium, respectively, the molten salt deposits may penetrate the alloy surface and enhanced sulphur activity in this subsurface region gives rise to the precipitation of a continuous sulphide layer.

     Specific to in-service, polycrystalline nickel components under hot corrosion fatigue conditions, examples have been reported where chromium- and titanium-rich sulphide particles have precipitated at subsurface grain boundaries in preference to forming the continuous sulphur-rich zone.3, 4 Future superalloy developments, required to resist such Type II damage, must incorporate an accurate assessment of fatigue behavior under representative operating conditions.5 This is extremely challenging in the laboratory setting; however, previous papers have reported the design of in situ environment test cells for the assessment of structural metals under hot sulphur-bearing environments.6

     From the perspective of mechanical behavior and fatigue in particular, hot corrosion may be especially problematic should the corrosive attack lead to the development of localized surface pits. Recent studies have evaluated the fatigue strength of alternative nickel superalloys subjected to pre-existing pitting damage,7, 8 and this supports the ranking

of alloys based on environmental resistance. However, there remains a fundamental requirement to understand the role of cyclic stress on pit formation, the stress raising effect of corrosion pits, and the influence of hot corrosive environments on fatigue crack initiation and subsequent crack growth.

     In the example of compressor or turbine rotor components, the precise form and location for hot corrosion pitting may be controlled by various factors. These include pre-existing geometric features, surface treatments, inherent gas composition, surface contaminants (e.g., ingested salts), and the substrate microstructure. To simulate these service conditions, specialist test equipment and procedures have been designed for the assessment of laboratory scaled test coupons.9 Such systems need to address the surface preparation of specimens, pre-salting, prolonged isothermal heating, and mechanical loading under low and high cycle fatigue waveforms. Specific experiments may be conducted to characterize fatigue strength or fatigue crack growth to partition initiation and damage-tolerant behavior under hot corrosion environments.

     In this study, fatigue strength was measured from plain cylindrical, shot peened specimens exposed to a SO2 gas environment at 700°C to provide a “baseline” SN curve. Under these circumstances, the corrosion damage was accumulating concurrent with cyclic loading. This performance was then compared with specimens with pre-corroded pitting, either with the surface corrosion products fully retained or after a cleaning operation. Indeed, the response to various cleaning reagents and procedures formed a wider ranging objective of the present study.

     All the scenarios described here are relevant to the design, operation, and lifing of critical rotating engine components. The experimental study was defined to support existing damage-tolerant component lifing methods. Recognizing that the total fatigue life measured in the low cycle fatigue (LCF) experiments represents a combination of initiation life and crack propagation, data from “long” crack growth testing will be presented to help partition the relevant importance of these different stages of damage and any unique consequences of crack growth under a hot corrosion environment. These include characterization of Stage II “Paris” crack growth together with an assessment of fatigue crack growth threshold behavior.



     It is recognized that the transition from a corrosion pit to a true fatigue crack is highly complex, incorporating the effects of “small” and “short” scale growth during the early stages of crack development. Previous authors have monitored and evaluated the behavior of environmentally assisted short crack growth behavior in alternative alloys and in relatively benign aqueous environments at ambient temperatures.10, 11 However, the current investigation of high-temperature corrosion fatigue behavior was not intended to enable such characterization.

2 EXPERIMENTAL METHODS

     The current investigation focussed on the nickel-based superalloy RR1000 in fine-grained microstructural form. Plain cylindrical and corner crack test specimens were machined from a RR1000 forging. Proprietary thermomechanical processing and heat treatment had generated a standard fine-grained microstructure with an average grain size of 8 μm plus trimodal distribution of γ′ strengthening particles (i.e., coarse primary γ′ particles decorating the grain boundaries, with finer scale secondary γ′ and tertiary γ′ precipitates evenly distributed inside the grains). The grain size was measured using a standard line intercept method applied to multiple two-dimensional (2D) digital images (ASTM E112-10). The typical γ/γ′ microstructure is illustrated in Figure 1; however, much greater detail on RR1000 thermomechanical processing and microstructural evolution, including resolution of the secondary and tertiary γ′ particles, has been previously published by Mitchell et al.12




              FIGURE 1Open in figure viewerPowerPoint

              Fine-grained microstructure in RR1000. Near-equi-axed γ grains (light regions) with γ′ particles

Corrosion surface morphology-based methodology for fatigue assessment of offshore welded structures — Victor Okenyi et al., 2023

1 INTRODUCTION

     Offshore wind energy generation can reduce the carbon footprint as there is a worldwide move towards installing more renewable energy capacity through offshore wind turbines (OWTs). Improving OWT structural performance can reduce costs associated with operation and maintenance. Structural performance must be closely researched with the global offshore wind energy expansion trend. In the United Kingdom, monopile supports (fixed-bottom OWT) are widely used due to installation convenience.1 OWTs are subjected to cyclic loads from winds and waves. They operate in one of the harshest environmental conditions, making them vulnerable to fatigue damage accumulation. The wind energy market has seen continuous growth globally.2 As the renewable energy sector grows, high-rated OWTs are deployed deeper into seawater,3, 4 where combined effects of cyclic mechanical loads and corrosion can create a detrimental effect. The design longevity and safety of OWTs, particularly their support structures, are crucial given their 20-year lifespan, considering that they can be in deep-sea subject to seawater corrosion. With many already nearing end-of-life OWTs, a comprehensive assessment of the fatigue life of offshore welded structural steel incorporating corrosion morphology effects is essential to reduce regular in-service inspections, ensure durability, and maintain operational efficiency. This justification underscores the need for thorough fatigue life analysis in offshore materials to ensure longevity and safety.

     OWT monopiles are often constructed from welded hot-rolled structural steel plates, and their fatigue performance has been reported to be superior compared to normalized offshore steel.5, 6 Fatigue assessment factors such as defects caused by welding, oscillating stresses due to environmental loads, high stress concentrations at the intersection, and pits from corrosion due to seawater have been studied.7-11 OWT monopiles are joined with V-shaped butt welds on both sides. The welding quality can significantly affect the fatigue performance of OWT monopiles as cyclic stresses at the welds can initiate fatigue cracks, particularly in the heat-affected zone (HAZ).12 Manufacturing defects and residual stresses, stress concentration factor (SCF) at welds, surface roughness, and corrosion pitting at the surface are vital in the high cycle fatigue performance in offshore conditions. There is a need for all these fatigue-influencing factors to

be holistically investigated to develop an improved way of assessing the fatigue life of offshore structures. The stress versus number of cycles (S-N) curve approach has been predominantly used to predict fatigue life,13-15 and it has also been used in damage tolerant approaches.16, 17

     The fatigue capacity of structural steels in offshore applications is affected by various parameters, each of which can influence the quality and the mechanical properties. Although there are many reports on fatigue testing on structural steels, this review covers a representative number of studies18-47 focusing on S355 butt-welded structural steels. These structural steels have been tested using a variety of test setups, loading conditions, welding types, and other postprocessing variables. The tested specimens have been subjected to various load-controlled fatigue conditions, including rotational bending, axial and bending fatigue testing at stress ratios of R = −1, 0, 0.1, 0.5 and different frequencies. The fatigue properties were affected by the surface roughness, the type of applied welding, the quality of the weldments, hardness, the thickness of the tested specimens, and the consideration of the environment (air or corrosive) for the fatigue tests. The predominant structural steel that has been taken into consideration is S355. In addition, the review has also considered other structural steels with the same range of yield strength and ultimate tensile strength (UTS).

     The average UTS for S355 steel was found to be 546 MPa, whereas the average yield strength was 412 MPa. The fact that some of the reported hardness values were within a specific range suggests that the testing was carried out from the base material to the weld zone, including the HAZ. The highest reported values were found to be at the weld region. For S355 steel grades, the elongation was in the range of 16.6%–36%. Metal active gas (MAG) welding and submerged arc welding (SAW) were the most common welding methods. Arc welding methods generally have been widely used in offshore structures, particularly in OWT.48, 49

     In addition to the reviewed literature,18-

47 S-N data from the design code standards BS7606,50 DNVGL-RP-C203,51 BS-EN1993-1-9,52 and IIW recommendations53 were also considered. The codes provided S-N curve values in both air and corrosive conditions in artificial seawater (ASW) and salt spray chambers (SSC). Welded specimens with one-side weld, usually of smaller thickness, appear to have better fatigue strength than two-side butt weld. In contrast, specimens without a weld have significantly superior fatigue life. This is consistent with the well-known fact that the weld zone generates a discontinuity in the material, and it is frequently sensitive to local stresses from which cracks typically initiate.54 The high-frequency mechanical impact (HFMI) and shot peening (SP) treated specimens demonstrate that both post-weld treatment procedures enhance the fatigue life of structural steels. Identical specimens tested in SSC and ASW with the same stress ratio showed comparable fatigue performance in corrosive environments. However, compared to specimens tested in air, it was observed that corrosion negatively influenced the fatigue life of welded structural steel. Also, from the collected literature of fatigue tests in air and corrosive environments, it was observed that corrosion contributed to approximately 16% reduction in the fatigue strength of S355 structural steel.

     The surface morphology of corroded offshore structures operating under seawater corrosion can be crucial. Pitting exists in the early life stages of marine structures, and it can be challenging to observe. Research showed that surface roughness of corroded carbon steel changed over time, and corrosion surface morphology can be quantified into shallow pits, overlapping pits and uniform corrosion stages.55 Also, significant volumetric changes are observed over time, signifying the transition from pits to more uniform corrosion. Deep pits show higher stress concentrations, and the characteristics of corrosion pits or localized corrosion behavior can be fundamentally understood through skewness and kurtosis assessments.56, 57

     Statistical analysis of the probability distributions have been employed as a valuable tool in understanding corrosion pits, which also involved time. This research establishes a connection between the pit characterization, the localized stresses, and its relationship to cyclic loading under corrosive conditions. The pragmatic use of the S-N curve concept

An accelerated corrosion-fatigue testing methodology for offshore wind applications — Ali Mehmanparast et al., 2021

In 2019, the global offshore wind installed capacity reached a new record of 30,000 MW [1] , which is about twice the installed capacity in 2016. Knowing that several projects for large offshore wind farms have been launched and new farms are under construction, such as the expansion of the Hornsea project in the UK, the exponential growth in offshore wind capacity is expected to continue in the coming years. The majority of the installed offshore wind turbines (i.e. over 80%) are supported by monopile foundations while the remaining minority are supported using other types of foundations including jackets [2] . The offshore wind farms are typically designed for 20 to 25 years of operation under extreme loading conditions due to the constant exertion of wind, wave and current loads which induce fatigue damage in the installed structures [3] . As the first generation of offshore wind farms which were installed in the late 1990s and early 2000s are quickly approaching their end of initial design life, questions are being raised regarding the realistic estimate of the remaining life of the installed offshore wind turbines by considering the over-conservative assumptions employed during the design process. This means that the offshore wind monopile foundations could presumably operate for a longer period, hence studies are being conducted on the possibility of life extension for existing wind farms rather than decommissioning the offshore wind infrastructure upon reaching the end of initial design life.
In this context, it is important to understand the behaviour of materials employed in fabrication of monopiles under fatigue loading conditions in air and seawater environments [4] . The fatigue tests must replicate the operational loading conditions, meaning the wind and wave spectra as well as the rotational intervals of the rotor must be considered in the test design. The SLIC (Structural Lifecycle Industry Collaboration) joint industry project was recently formed with the overall aim of achieving a better understanding of fatigue and fracture behaviour of offshore wind monopiles, particularly in air [5] . While performing fatigue tests in air are relatively simple, corrosion-fatigue tests are often conducted in artificial sea water prepared in accordance with ASTM D1141 “Standard Practice for the Preparation of Substitute Ocean Water” recommendations [6] . Corrosion-fatigue tests for offshore wind applications are typically performed at 0.1–0.3 Hz to account for wave excitation frequency [7] . The low frequency range in corrosion-fatigue tests results in a low number of cycles per unit of time. This means that

a longer period of time is required in order to achieve a certain number of cycles in corrosion-fatigue tests, hence these tests take much longer to complete compared to higher frequency tests in air.
It is known that for a given material, loading condition and surface finish (in the case of welded joints), the fatigue damage in air is dependent on the number of cycles. Therefore, an effective approach to shorten fatigue experiments in air is to increase the test frequency. Although cyclic testing at higher frequencies can effectively reduce the amount of time needed to conduct fatigue tests in air, this approach cannot be applied to corrosion-fatigue tests due to the low test frequencies required for such tests in seawater. In other words, corrosion-fatigue damage is dependent on the number of cycles (which drives the fatigue damage) as well as time (which drives the corrosion damage). Therefore, increasing the frequency in corrosion-fatigue tests would discard the contribution of corrosion damage to the overall failure, and consequently the results from corrosion-fatigue tests at high frequencies would be very similar to those results obtained from the fatigue tests in air.
While the increase in frequency cannot be used as an acceleration mechanism in corrosion-fatigue tests, the experimental data available in the literature indicate that an increase in seawater temperature, would reduce the fatigue life and increase the crack growth rate [8] . Therefore, the main aim of this study is to explore the influence of temperature on the fatigue performance of engineering material and subsequently develop an accelerated test method for performing corrosion-fatigue tests in much shorter time scales. In order to achieve this goal, the fatigue test data at different temperatures on various materials have been collated and analysed in this study and new models have been proposed to quantify the extent of acceleration in uniaxial S-N fatigue and fracture mechanics-based fatigue crack growth tests in seawater by changing the test temperature. The results have been discussed with a view to proposing a novel corrosion-fatigue acceleration mechanism by increasing the temperature in seawater corrosion-fatigue tests and suggest a practical approach to enhance the corrosion-fatigue life predictions for offshore wind turbine monopile foundations.
The material used in the fabrication of offshore wind monopile foundations is mainly S355 structural carbon steel [4] . Although corrosion protection mechanisms by means of surface coating and cathodic protection are considered in the design of offshore wind turbine foundations, which are the parts of the structure in direct contact with seawater, such corrosion

protections normally break down after a certain duration of operation and subsequently corrosion damage occurs in the offshore wind turbine foundations before the corrosion protections are repaired. The corrosion mechanism is the result of an electrochemical reaction to a transfer of one or several electrons taking place in two stages; the anodic and cathodic half-reaction. During the process, electrons transit from the anode to the cathode [9] . Two half-equations (anodic and cathodic) which describe the chemical reactions during the corrosion process in steels employed in offshore wind turbine foundations are given below: (1) Fe → Fe 2+ + 2 e − (2) O 2 + 2 H 2 O + 4 e − → 4 OH −
Thus, the resulting reactions from the combination of those two half-reactions, which leads to creation of the rusts, are: (3) 2 Fe + O 2 + 2 H 2 O → 2 Fe + 4 OH – = 2 Fe(OH) 2 (4) 4 Fe(OH) 2 + 2 H 2 O + O 2 → 4 Fe(OH) 3 = 2 Fe 2 O 3 (H 2 O) + 4 H 2 O
Therefore, the resumed chemical reaction which occurs during the corrosion of steel is: (5) Fe + 3 O 2 + 2 H 2 O = 2 Fe 2 O 3 (H 2 O)
As it can be seen above, the presence of oxygen within the seawater is necessary for the corrosion damage to happen. Nonetheless, in the case of a fully immersed steel-made structure, a corrosion mechanism will still occur in the absence of dissolved oxygen but at a slower rate. In fully immersed offshore wind turbine foundations, the cathodic reaction would be replaced by a hydrogen reduction by: (6) 2H + + 2 e − → H 2
Corrosion damage is known to be very sensitive to the temperature. The temperature dependency in the corrosion process is due to the fact that the dissolution of the metal (anodic reaction) is activated by increasing the temperature, whilst the reduction of oxygen (cathodic reaction) is slowed down. Therefore, increasing the temperature reduces the solubility of oxygen in water, and therefore prevents the cathodic reaction from taking place [10] .
Offshore structures are subjected to cyclic service loading conditions which would introduce

Fatigue of X65 steel in the sour corrosive environment—A novel experimentation and analysis method for predicting fatigue crack initiation life from corrosion pits — Farnoosh Farhad et al., 2021

1 INTRODUCTION

     API-5L Grade X65 steel are commonly used to manufacture pipelines used to convey production fluids extracted by the oil and gas industry.1, 2 The mechanical properties, cost, and availability are the main factors that determine the selection of steel. However, despite having modest resistance to uniform corrosion, this grade of steel is prone to localized corrosion (pitting) upon exposure to sour corrosive environments,3, 4 typical for many mature oil and gas reservoirs. The sour corrosive media can reduce the fatigue life of pipelines under the cyclic load5 applied from sea waves, seabed movements, and internal pressure variation.6 In order to increase operational safety and minimize the likelihood of pipelines failures, a better informed and more efficient maintenance and inspection schedule is required. A vital prerequisite on the path to meet these goals is the development of a more reliable fatigue life prediction model.

     The presence of corrosion pits has been cited as main contributory factor in many failures of pipelines reported by the oil and gas industry.2, 3 Corrosion pits are a form of localized corrosion that can jeopardize the life of engineering assets by accelerating material loss over a small area or by increasing the risk of crack initiation as a stress riser. A major part of the total fatigue life comprises the transition of corrosion pit to fatigue cracking,7 the so-called pit-to-fatigue crack transition that has received growing attention in recent research publications.8 Different models exist in the literature to predict crack initiation life from corrosion pit,9-14 which are based on linear elastic fracture mechanics (LEFM) criteria. This criterion predicts the behavior of the long crack by considering corrosion pit as a pre-existing short crack and disregards the crack initiation regime which is quite a significant regime in high cycle fatigue life. The model proposed in this paper for predicting the crack initiation life from corrosion pit in a sour environment considers pits as a stress concentration zone, that is, a notch, and predicts short crack initiation life. This model uses the data obtained from environmental fatigue testing that replicates sour conditions present in service.

     Previous studies have described fatigue tests performed in air or environmental fatigue tests conducted in benign environments10, 14-

17 investigating the effect of the presence of corrosion pits. In earlier publications18, 19 we have summarized the discrete parts of our initial efforts toward developing a harmonized approach to environmental fatigue testing of alloys. Prior to our work, there were no reports of small-scale corrosion fatigue tests of alloys exposed to toxic H2S containing fluids, because of the test complexity and health and safety considerations. In this paper, we detail the overall approach for the first time and present new data concerning the effect of sour environments on fatigue behavior of materials using small-scale standard samples.
2 EXPERIMENTAL

        2.1 Material and specimens

        The material of interest in this study is seamless API-5L X65 grade pipeline steel provided by the industrial sponsor. The chemical composition was obtained by optical emission spectroscopy at The Welding Institute (TWI Ltd.) reported in previous work20 and the cyclic and monotonic mechanical properties required in this paper were obtained from the literature7 as reported in Table 1. The chemical composition of tested material is reported in Table 2.






           TABLE 1.
            Mechanical properties of API-5L-X65 used in this study7














                       Elastic modulus, E(GPa)

                       211




                       Yield strength, YS (MPa)

                       516

Crack growth direction effects on corrosion-fatigue behaviour of offshore wind turbine steel weldments — Anais Jacob et al., 2021

Crack length
Initial crack length at the beginning of pre-fatigue cracking
Initial crack length at the beginning of the main fatigue test
Final crack length at the end of the main fatigue test
Normalised crack length
Fatigue crack growth rate
Ramberg-Osgood non-linear stress coefficient
Specimen thickness
Paris-law coefficient
Elastic Young's modulus
Frequency
Stress intensity factor range
Stress intensity factor corresponding to P m a x
Stress intensity factor corresponding to P m i n
Paris-law exponent
Ramberg-Osgood non-linear stress exponent
Number of cycles
Maximum applied load
Minimum applied load
Load range
Plastic zone size
Specimen width
Strain
Applied stress
Yield stress
Back face strain
Base metal
Compact tension
Electrical discharge machining
Fatigue Crack Growth
Heat Affected Zone
Linear elastic fracture mechanics
Offshore wind turbine
Residual stress
Submerged Arc Welding
Stress Intensity Factor
Weld metal
Renewable energy is a reliable source of clean energy, which helps the international community to tackle greenhouse gas emission issues and contributes to meeting the increasing energy demand in the world. Among the different sources of renewable energy, offshore wind has become one of the most preferred solutions in recent years due to its large-scale deployment potential and significant reductions in its levelised cost, especially since 2016 [ [1] , [2] , [3] , [4] , [5] , [6] ]. The offshore wind turbine (OWT) installation, operation and in-service condition monitoring require consideration of a range of issues associated with the design and assessment of these structures. Indeed, due to the offshore turbulence and cyclic loads from wave, wind and current, these offshore structures are subjected to fatigue damage [ 7 ]. Moreover, for the OWT foundation, which is in direct contact with seawater, the additional environmental damage due to corrosion must also be considered and accounted for in design and life assessments. In order to withstand the critical conditions in harsh environments, the structural integrity of OWTs needs to be carefully assessed to provide a reliable estimate for the remaining life of these structures.
Among different types of existing OWT support structures, the monopile is the most popular foundation type which is widely used in shallow water offshore wind farms and has great design advantages as well as minimal footprint on the se

abed [ 8 , 9 ]. Typical dimensions for the OWT monopile range from 50 m to 70 m in length, 3 m–10 m in diameter and 40 mm–150 mm in wall thickness [ [10] , [11] , [12] ]. Monopiles are installed by driving them into the seabed; hence the structure should withstand the hammering loads during installation which vary from site to site depending on the soil conditions. During operation in harsh offshore environments, monopiles are subjected to wind, wave and sea current cyclic loads, therefore they have to be designed for a certain fatigue life with suitable safety margins against failure. Moreover, they have to be designed to withstand the horizontal and vertical loads acting on the entire assembly, including the transition piece, tower and wind turbine blades. The manufacturing procedure for offshore wind monopile structures consists of rolling and bending large structural steel plates and subsequently welding them together in longitudinal and circumferential directions [ 13 ]. The design, fabrication and inspection of OWT monopile foundations are costly. Therefore, an important challenge for the offshore wind industry is to improve the current best practice for the structural design and integrity assessment of monopiles that are operating in the harsh offshore environments with constant exertion of wind and wave loads inducing corrosion-fatigue damage, particularly at the weld regions and in the presence of welding residual stresses (RSs). Materials used in offshore structures are mainly chosen from medium to high strength structural steels, with the yield stress values typically ranging from 275 to 460 MPa, due to their suitable mechanical properties and low cost [ 14 ]. The studies in the literature have shown that fatigue crack initiation and growth primarily occur at the weld toe, for the as-welded conditions, and at circumferential welds [ 6 ]. Depending on the welding procedure, the crack may propagate from the Heat Affected Zone (HAZ) into the Base Metal (BM) in the through thickness direction [ 6 ]. More information about the fatigue damage and loading analysis of the monopile foundations can be found in Ref. [ 15 , 16 ].
An inter-laboratory test programme (referred to as the Structural Lifecycle Industry Collaboration Joint Industry Project-SLIC JIP) was previously run to characterise the fatigue crack growth (FCG) behaviour of the monopile welded structures in both air and seawater in order to better estimate the remaining life of monopiles in the presence

of fatigue cracks [ 6 , 17 ]. The primary focus of the SLIC project was on S355 G8+M steel; however, there is an essential need to extend the experimental investigations to other sub-grades of steel that are employed in the fabrication of monopiles and compare their FCG behaviour with those obtained from S355 G8+M steel in Ref. [ 6 ]. In the current study, the FCG behaviour of S355 G10+M structural steel, which is another sub-grade of steel that is widely used in the fabrication of monopiles, has been experimentally investigated in a seawater environment and the results have been compared with the material's behaviour in air as well as corrosion-fatigue crack growth behaviour in other steels. The results obtained from this study provide a better understanding of the FCG behaviour of a wide range of steels and facilitate structural design and integrity enhancement of OWT monopiles in free-corrosion conditions.
The material used in this study is EN-10225:09 S355 G10+M, which is widely used in the fabrication of offshore structures including OWT monopiles, as explained in the Standard from Det Norske Veritas [ 14 ]. In S355 G10+M notation, the letter S indicates that the material employed in this study is a structural steel with a minimum yield stress of 355 MPa while G10 indicates the steel grade within the material groups specified in the EN-10225 standard and +M indicates the thermo mechanical rolling process. The multi-pass submerged arc welding (SAW) technique was used to fabricate a double V-grooved welded plate with a thickness of 90 mm. The solid wire electrode was EN ISO 14171-A (EN 756): S3Si and the chosen flux was EN ISO 14174: SA FB 1 55 AC H. Welding was conducted parallel to the rolling direction using run off, thereafter cut, at each end of the plate, as shown in Fig. 1 (a). The BM plates were hot-rolled prior to welding and individual weld passes at each V-groove were applied with a pre-heat of 60 °C. Welding was conducted using three electrode wires providing a heat input of up to 3.0 kJ/mm and an inter-pass temperature of not more than 250 °C. Double V-groove welding was performed unevenly by initially filling the first mach

🧪 Chemical Profile: nitric acid

IUPAC Name: nitric acid
PubChem CID: 944

📐 Computed Local Properties (RDKit)

Could not resolve a valid SMILES string for RDKit analysis.

🌡️ Experimental Properties (PubChem)

• Boiling Point: 181 °F at 760 mmHg (NIOSH, 2024)

⚠️ Experimental Hazards (PubChem)

• H272: May intensify fire; oxidizer
• H290: May be corrosive to metals
• H302: Harmful if swallowed
• H304: May be fatal if swallowed and enters airways
• H314: Causes severe skin burns and eye damage
• H318: Causes serious eye damage
• H330: Fatal if inhaled
• H331: Toxic if inhaled
• H370: Causes damage to organs
• H372: Causes damage to organs through prolonged or repeated exposure
• H402: Harmful to aquatic life

Research will be limited to:
- Concentration: 3% Nitric Acid
- Solvent: Ethanol
- Topic: Chemical Safety/Hazards
- Scope: Mixing/Reaction of the Specified Chemicals

Strategy: The user is asking about the safety of a specific chemical mixture: 3% nitric acid in ethanol. This mixture is commonly known in metallurgy as 'Nital'. While 3% is a standard concentration for etching, mixing a strong oxidizer (nitric acid) with a flammable fuel (ethanol) is inherently risky. I need to identify the specific hazards, including the 'induction period' (delayed reaction), potential for gas evolution/pressure buildup, and the risk of explosion if the concentration increases or if it is stored improperly. I will focus on professional safety data sheets (SDS) and metallurgical laboratory guidelines.
Queries:
- safety of 3% nitric acid in ethanol nital solution hazards
- nitric acid ethanol reaction induction period explosion risk
- storage and disposal of nital etchant 3% nitric acid ethanol

🔍 Reading and summarizing 5 new websites...

1. [PDF] Safety Data Sheet - PACE Technologies
2. [PDF] Nital Solution (NI2010SS) - Safety Data Sheet
3. [PDF] Safety Data Sheet: Etchant Nital - Carl ROTH
4. [PDF] Alcoholic nitric acid ~ 10% (Nital) - Morphisto
5. [PDF] SAFETY DATA SHEET NITAL 3%

Found 5 websites. Summarized content:

[PDF] Safety Data Sheet - PACE Technologies
The Safety Data Sheet from PACE Technologies describes the hazards associated with Nital Etchant, which contains ethanol and nitric acid. While the exact concentration of nitric acid varies (1-8%), this information is still relevant for a 3% concentration.

Key Safety Information for mixtures of Ethanol and Nitric Acid (as Nital):

• Hazards: Flammable liquid and vapor, oxidizer (may intensify fire), corrosive (causes severe skin burns and eye damage), harmful if swallowed, toxic to aquatic life, causes damage to organs.
• Precautionary Statements:
  • Keep away from heat, sparks, open flames, and hot surfaces - No smoking.
  • Keep/Store away from clothing and combustible materials.
  • Take any precaution to avoid mixing with combustibles, strong bases, metallic powders, carbides, hydrogen sulfide, turpentine, and combustible organics.
  • Keep container tightly closed.
  • Use explosion-proof equipment.
  • Take precautionary measures against static discharge.
  • Do not breathe vapors/spray.
  • Wear protective gloves/clothing/eye protection/face protection.
• Emergency Overview: Poison, Danger! Corrosive. Liquid and mist cause severe burns. Oxidizer. Contact with other material may cause fire. May be fatal if swallowed. Harmful if inhaled. Vapor harmful. Flammable.
• Health Effects:
  • Inhalation: Corrosive, may cause irritation, pneumonia, or pulmonary edema.
  • Ingestion: Corrosive, may cause burns to the mouth, throat, esophagus, and gastrointestinal tract.
  • Skin Contact: Corrosive, may cause redness, pain, and severe burns.
  • Eye Contact: Corrosive, vapors are irritating, may cause severe burns and permanent eye damage.
• Fire Fighting: Flammable liquid and vapor. Use water spray, dry chemical, alcohol foam, or carbon dioxide. Water may be ineffective.
• Incompatibilities: Strong oxidants, silver salts, acid chlorides, alkali metals, metal hydrides, hydrazine, strong bases, metallic powders, carbides, hydrogen sulfide, turpentine, and combustible organics.
• Exposure Limits: OSHA PEL for Nitric Acid: 2 ppm (TWA); ACGIH TLV: 2 ppm (TWA), 4 ppm (STEL). Ethanol: OSHA PEL 1000 ppm (TWA); ACGIH TLV 1000 ppm (TWA).
• First Aid: Immediate first aid is important to reduce the health effects of the substance. Recommendations exist for inhalation, ingestion, skin contact, and eye contact.
• Reactivity: The mixture has a moderate reactivity hazard (Rating 2).

This SDS indicates that mixing even small concentrations of nitric acid with ethanol poses significant hazards due to flammability, corrosivity, and potential for dangerous reactions. Appropriate precautions and personal protective equipment are crucial.

[PDF] Nital Solution (NI2010SS) - Safety Data Sheet
Based on the provided Safety Data Sheet (SDS), mixing 3% nitric acid in ethanol poses several safety hazards:

• Flammability: The solution is a flammable liquid and vapor.
• Oxidizer: The solution is an oxidizer and may intensify fire. Avoid mixing with combustibles.
• Corrosivity: The solution causes severe skin burns and eye damage.
• Reactivity: The SDS states that a concentration greater than 10% nitric acid in flammable solvent such as alcohol can create highly explosive mixture. The concentration is less than 10% at 3% nitric acid. Nitric acid and alcohol solutions can generate fumes.
• Handling Precautions: The SDS recommends using the solution in well-ventilated areas, avoiding splashes or sprays, keeping it away from heat and ignition sources, wearing protective equipment (gloves, clothing, eye/face protection), and using non-sparking tools. Ground/bond containers.
• Storage Precautions: Store in a cool location, avoid combustible materials, ignition sources or open flame. Must be stored locked up. The storage area should be vented or well-ventilated.

The SDS refers to the solution as "Nital Solution," and the specific SDS analyzed describes a solution containing 17.536% Nitric Acid and 82.464% Ethanol. While this is of a higher concentration than the user's stated 3% nitric acid request, the SDS does note in Section 7 that "Nital (nitric acid and alcohols) should be used in concentrations no greater than 10% nitric acid by volume." The hazards described in the SDS are still applicable to a lower concentration, albeit potentially less severe. The SDS also states that lengthy storage could lead to evaporation of alcohol, thus increasing the concentration of nitric acid.

[PDF] Safety Data Sheet: Etchant Nital - Carl ROTH
Based on the provided Safety Data Sheet for "Etchant Nital 5%", which contains nitric acid and ethanol, here's a summary of the relevant safety information regarding mixing a 3% nitric acid solution in ethanol:

• Hazards Identification: The SDS identifies Etchant Nital 5% as a flammable liquid and vapor (H225), corrosive to metals (H290), and causing severe skin burns and eye damage (H314). It also contains supplemental hazard information, EUH071 which indicates that the product is corrosive to the respiratory tract.

• Composition: The mixture contains Ethanol (70-90%), 2-Propanol (5-10%), and Nitric acid ...% [C ≤ 70 %] (5 - <6%). The SDS emphasizes that nitric acid solutions require different classifications and labelling depending on concentration.

• Firefighting: The mixture is combustible, and in poorly ventilated areas, flammable/explosive vapor-air mixtures may form. Hazardous combustion products include nitrogen oxides, carbon monoxide, and carbon dioxide.

• Reactivity: The mixture contains reactive substances. Vapors may form explosive mixtures with air. Violent reactions can occur with strong oxidizers, alkali metals, alkaline earth metals, acetic anhydride, peroxides, phosphorus oxides, nitric acid, strong alkali, nitrate, and perchlorates, potentially leading to explosive properties.

• Handling: Requires sufficient ventilation. Keep away from ignition sources. Take precautionary measures against static discharge.

• Incompatibilities: Keep/store away from oxidizing substances and different metals

• Exposure Limits: Lists Occupational Exposure Limit Values (OELV) for nitric acid. For example for Malta, the OELV for nitric acid is 12.6 mg/m3.

The SDS suggests that while the document is for a 5% nitric acid mixture, it highlights the hazards associated with combining nitric acid and ethanol, and proper precautions should be taken, even with the requested 3% concentration. These precautions include ensuring sufficient ventilation, keeping the mixture away from ignition sources and incompatible materials, and using appropriate personal protective equipment.

[PDF] Alcoholic nitric acid ~ 10% (Nital) - Morphisto
Based on the provided Safety Data Sheet (SDS) for Alcoholic nitric acid ~ 10% (Nital) from Morphisto GmbH, here's a summary of the chemical safety aspects related to mixing nitric acid and ethanol, focusing on the hazards of this specific mixture. Note that the document explicitly discusses a mixture of these chemicals, not the isolated act of mixing for safety purposes, but the following deductions are relevant:

Key Hazard Information (Regarding a Nitric Acid and Ethanol Mixture):

• Classification: The mixture (Nital, ~10% nitric acid in ethanol) is classified under Regulation (EC) No 1272/2008 as:

  • Met. Corr. 1 (Corrosive to Metals)
  • Flam. Liq. 2 (Highly Flammable Liquid)
  • Skin Corr. 1B (Causes severe skin burns and eye damage)
  • Eye Dam. 1 (Causes serious eye damage). Note this document says "causes severe skin burns..." then "causes serious eye damage."

• Hazard Statements:

  • H225: Highly flammable liquid and vapour.
  • H290: May be corrosive to metals.
  • H314: Causes severe skin burns and eye damage.

• Precautionary Statements:

  • P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
  • P260 Do not breathe mist/vapours/spray.
  • P280 Wear protective gloves/protective clothing and eye protection/face protection.
  • P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
  • P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P310 Immediately call a POISON CENTER/doctor.

• Composition:

  • Ethanol: 80 - <85%
  • Nitric Acid: 10 - <15%
  • 2-Butanone: <1%

• Fire Hazards:

  • Highly flammable; vapours can form explosive mixtures with air. In case of fire, irritant gases/vapours, carbon monoxide, carbon dioxide, and nitrogen oxides may be liberated.

• Reactivity Hazards:

  • Vapours can form explosive mixtures with air.
  • Oxidizing agents, strong reducing agents, strong acids and strong alkalis are incompatable materials.

• Handling Precautions:

  • Use local exhaust ventilation.
  • Avoid breathing gas/fumes/vapour/spray.
  • Wear suitable protective clothing, gloves, and eye/face protection.

• Storage Precautions:

  • Keep container tightly closed and locked up.
  • Store in a cool, well-ventilated place, away from heat, sparks, and open flames.
  • Keep away from incompatible materials (oxidizing agents, pyrophoric/self-heating substances, explosives, flammable solids, etc.)

• Special Labeling: EUH071 Corrosive to the respiratory tract.

In summary: Mixing nitric acid and ethanol, even at the concentrations described, presents significant hazards, including flammability, corrosivity to skin, eyes and metals, and the potential for explosive vapour mixtures. Appropriate precautions, including PPE, ventilation, and storage away from incompatible materials, are essential.

[PDF] SAFETY DATA SHEET NITAL 3%
The Safety Data Sheet (SDS) describes NITAL 3%, a mixture containing ethanol (60-100%), methanol (1-5%), and nitric acid (1-5%). It's a flammable liquid (Flam. Liq. 2 - H225) and may cause damage to organs (STOT SE 2 - H371).

Hazards:

• Highly flammable (flash point 13-14°C). Keep away from heat, sparks, and open flames.
• Vapors may form explosive mixtures with air.
• May cause damage to organs. Do not breathe vapor/spray.
• Contains methanol, which is toxic.

Precautionary measures include:

• Keeping away from heat and ignition sources.
• Avoiding breathing vapor/spray.
• Wearing protective gear (gloves, clothing, eye/face protection).
• Using only outdoors or in a well-ventilated area.

The SDS includes first aid measures, firefighting information, accidental release measures, handling and storage precautions, exposure controls, and information on the physical and chemical properties of the mixture. It also provides toxicological and ecological information for the individual components: ethanol, methanol and nitric acid. Nitric acid causes severe skin burns and eye damage.

🧪 Protocol Master: ASTM/ISO procedures for stress concentration and corrosion fatigue in steel alloys without SEM setup

Method: Simulation validated (6 cycles) | Date: 2026-03-16

[!IMPORTANT]
User Constraints Enforced:
- No SEM setup allowed.

I. Materials & Equipment

• [ ] S355 Structural Steel alloy specimens
• [ ] Absolute Ethanol ($\ce{C2H5OH}$)
• [ ] Concentrated Nitric Acid ($\ce{HNO3}$)
• [ ] Deionized Water ($\ce{H2O}$)
• [ ] Silicon Carbide (SiC) grinding paper (240, 400, 600, 800, 1200 grit)
• [ ] 3-micron diamond suspension
• [ ] 0.05-micron colloidal silica slurry
• [ ] High-nap polishing cloth
• [ ] Ice bath
• [ ] Glass beaker (250mL)
• [ ] Glass stirring rod
• [ ] Glass pipette
• [ ] Stainless steel tongs
• [ ] High-pressure air line / warm air dryer
• [ ] Optical Microscope
• [ ] Full face shield
• [ ] Acid-resistant gloves
• [ ] Lab coat

II. Step-by-Step Procedure

Step 1: Prepare 100mL of 3% Nital etchant by placing a 250mL beaker containing 97mL of absolute ethanol into an ice bath. Once chilled, use a glass pipette to slowly drip 3.0mL of concentrated $\ce{HNO3}$ into the $\ce{C2H5OH}$ while stirring continuously with a glass rod.
- Note: Perform this step exclusively inside a certified fume hood.
- Note: Always add acid to alcohol, never the reverse.
- Note: Nital should not be stored in tightly sealed bottles for long durations due to $\ce{NO_x}$ gas evolution and pressure buildup.

Step 2: Secure the steel specimen in a polishing holder and perform mechanical grinding using 240, 400, 600, 800, and 1200 grit SiC paper under a steady stream of $\ce{H2O}$. Rotate the specimen 90 degrees between each grit transition.
- Note: Ensure previous scratch patterns are completely removed before progressing to the next grit.
- Note: Use moderate pressure to avoid inducing artificial mechanical twins or surface smearing.

Step 3: Transition to fine polishing using a high-nap cloth with a 3-micron diamond suspension, followed by a final polish with 0.05-micron colloidal silica slurry until a mirror finish is achieved. Rinse with ethanol and dry immediately with a high-pressure air line.
- Note: Immediate drying is critical to prevent flash rusting of the S355 alloy.

Step 4: Using stainless steel tongs, immerse the polished specimen into the chilled 3% Nital etchant for approximately 10 seconds with gentle agitation.
- Note: Chilling the etchant helps suppress the reaction rate for better control over grain boundary definition.

Step 5: Immediately transfer the specimen into a beaker of pure ethanol to neutralize the acid, followed by a deionized water rinse and drying with high-pressure warm air.
- Note: Incomplete neutralization will lead to over-etching and surface charring.

Step 6: Inspect the etched surface using an optical microscope at 100x and 500x magnification to characterize the ferrite-pearlite grain boundaries, stress concentration zones, and early-stage pit morphology.
- Note: Optical microscopy is sufficient for identifying the transition from corrosion pits to fatigue cracks if the surface preparation is of metallographic grade.

III. Troubleshooting & Common Failures

Derived directly from failed simulation attempts:

• ⚠️ Do not mix Nitric Acid and Ethanol at room temperature without cooling, as an 'induction period' can lead to a violent, runaway exothermic reaction.
• ⚠️ Avoid over-etching (exceeding 30 seconds), as this will blacken the surface and obscure fine micro-cracks or pit initiation sites.
• ⚠️ Do not skip grit sequences during polishing, as remaining deep scratches can be mistaken for fatigue cracks during optical analysis.
• ⚠️ Avoid using a SEM setup if standard ASTM E3 and E407 protocols are followed correctly; optical microscopy provides sufficient contrast for S355 microstructural analysis.