Stress corrosion cracking of stainless steels in chloride environments

It is thought to start with chromium carbide deposits along grain boundaries that leave the metal open to corrosion. The main drawbacks of stainless steels is that these alloys are sensitive to chloride induced localized attack like pitting and crevice attack and stress corrosion cracking. Stress corrosion cracking is a form of localized corrosion that. Duplex stainless steels dss with roughly equal amount of austenite and ferrite phases are being used in industries such as petrochemical, nuclear, pulp and paper mills, desalination plants, marine environments, and others. The boiling magnesium chloride test cracks materials with the nickel levels found in relatively resistant austenitic and duplex stainless steels, thus making comparisons and evaluations for many service environments difficult. This study was carried out to assess the effect of applied potentials on stress corrosion cracking scc of austenitic stainless steels ass. Stress corrosion cracking of duplex stainless steels in.

When stainless steels are fully immersed, it is rare to see chloride stress corrosion cracking at temperatures below 60 c 150 f. Stress corrosion cracking facts and how to reduce the. Stress corrosion cracking of type 321 stainless steels in. Intergranular stress corrosion cracking of welded steel twi. Influence of addition of a few anion types chromates, sulphates, molybdates and nitrates to chloride solution on pitting and chloride cracking of stainless steels has been reported 7,8,9,10,11,12,14,15. It occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions and high temperature. How to reduce the risk of stress corrosion cracking scc the risk of stress corrosion cracking scc can be minimized through plant and equipment design. Stainless steels with increased molybdenum have provided improved resistance to chloridestresscorrosion cracking in environments such as aqueous sodium chloride. These investigations would suggest the addition of these anions to. Stress corrosion cracking of highstrength steels in. Duplex stainless steels offer several advantages over the common austenitic stainless steels. It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. When the cor rosion rate is of the order of less than 0.

Corrosion resistance of the austenitic chromiumnickel stainless steels in chemical environments interpreting corrosion test data the quantitative data secured in corrosion tests are often of a very low order of magnitude. Chloride induced cracking of stainless steels, caustic cracking of plain carbon steels, and ammonia damage to copper alloys are typical examples of this problem. Amaya h, kondo k, taniyama a, sagara m, ogawa k, murase t, hirata h, takabe h and ueda, m. The impact of scc on a material usually falls between dry cracking and the fatigue threshold of that material.

Potential chlorideinduced stress corrosion cracking of austenitic stainless steel and maintenance of dry cask storage system. Smithells metals reference book, 6th edition, brandes, 1983. Chloride stress corrosion cracking cscc is a type of intergranular corrosion. In aqueous chloride environments austenitic stainless steels and many nickel. Stresses can occur for a variety of reasons, including welding, physical damage, forming, machining, grinding, heat treatment, and operating stresses.

In the hydroiodic acid at temperatures exceeding 177oc, alloy b2 was sensitive to transgranular stress corrosion cracking. Click stress corrosion cracking scc is an environmentally wellknown as a. Stress corrosion cracking of duplex and super duplex. The environmental factors that increase the cracking susceptibility include higher temperatures, increased chloride content, lower ph, and higher levels of tensile stress. The duplex grades are highly resistant to chloride stress corrosion cracking, have excellent pitting and crevice corrosion resistance and exhibit about twice the yield stength as conventional grades. Selection of stainless steels for handling sodium hydroxide naoh sodium hydroxide caustic soda is a strong base, used widely for cleaning metals. Type 304l in a potentiostatically controlled chloride. There can be a risk of stress corrosion cracking scc attack at higher temperatures. Chloride stress corrosion cracking clscc is a type of stress corrosion cracking scc and is one of the most well known forms of scc in the refining and chemical processing industries. In sour service, resistance to stress corrosion cracking, pitting and crevice corrosion in the presence of cosub 2 and hsub 2s is required. Stress corrosion cracking scc stress corrosion cracking scc is the cracking induced from the combined influence of tensile stress and a corrosive environment. For a given alloy however there are many more environments that do not cause stress corrosion than those that so act. Avoiding stress corrosion cracking of carbon low alloy and.

Stress corrosion cracking of an austenitic stainless steel. The stress corrossion behavior of aisi type 304 stainless steel was investigated as a function of the environmental variables, temperature, ph, cation species, and chloride concentration in concentrated solutions of mgcl 2, cacl 2 and licl the time to failure at a constant stress, chloride ion concentration, and temperature increased in the order mgcl 2, cacl 2, licl. Stress corrosion cracking of austenitic stainless steels in chloride. The relative superiority of duplex stainless steels dss over austenitic grades with regards to stress corrosion cracking scc is discussed.

Chloride stress corrosion cracking clscc is one the most common reasons. The most common type of stress corrosion cracking in stainless steels occurs in chloride environments, which will be the focus of this discussion. Selecting alloys for severely corrosive environments. The most common type of stress corrosion cracking in stainless steels occurs in chloride environments, which will be the focus of.

Service experience has shown that duplex stainless grades have provided more resistance than that of cartech 316 stainless steel. Avoiding stress corrosion cracking of carbon low alloy and austenitic stainless steels in chloride and caustic environments synopsis this maintenance best practice guide is concerned with the performance of carbon and low alloy steels, and austenitic stainless steels, in chloride and caustic containing fluids. The susceptibility to stress corrosion cracking scc of type 321 stainless steel type 321s in a simulated petrochemical process environment containing hydrogen sulfide and chloride 20 wt. Stress corrosion crack growth behavior of 4 uns g40 and 4340 uns gg43400 steels was examined as a function of temperature in deaerated distilled water and deaerated 0. It can lead to unexpected sudden failure of normally ductile metals. Chloride stress corrosion cracking in austenitic stainless steel. The most common type is transgranular stresscorrosion cracking, scc, that may develop in concentrated chloridecontaining environments. This diagram figure 1 is analogous to a similar diagram for caustic. The higher alloyed duplex stainless steel alloys, ones with significant molybdenum and. Three underlying factors must be present to cause scc. All three families of the highperformance stainless steels will deliver a wide range of resistance to chloride pitting and stress corrosion cracking superior to that of types 304 and 316. Key corrosion mechanisms explained stainless steel world. It can be detrimental to austenitic stainless steels, one of the main reasons these steels are not considered a cureall for corrosion problems.

Chloride stress corrosion involves selective attack of a metal along its grain boundaries. Several chapters are spent on those special forms of corrosion that are investigated in the great detail in stainless steels, namely, pitting corrosion, crevice corrosion, and stress corrosion cracking. The scc propensity of austenitic stainless steels in marine environments is affected by many variables including the amount of moisture and time of wetness, airborne contaminants e. Although this list of environments that have been shown to promote stress corrosion cracking may appear extensive it is by no means exhaustive. Metalenvironment combinations susceptible to cracking are specific. Stress corrosion cracking of duplex stainless steels. Chloride stress corrosion cracking in austenitic stainless. The corrosion of duplex stainless steels in sour service.

Stress corrosion cracking of ldx 2101 duplex stainless. The actual pitting corrosion phenomenon is shown on propeller shaft of high speed craft, and the pit depth was measured with dial. Stainless steel bellows which typically have high stress levels come in contact with chloride contaminated environments especially during down time. However, many dss grades have been reported to undergo corrosion and stress corrosion cracking in some aggressive environments such as chlorides and sulfidecontaining. Stress corrosion cracking behavior of nickel base alloys. The mechanism of scc is shown as a simple representation in figure 1. Schematic view of stress corrosion cracking scc and corrosion fatigue cracking. Chloride stress corrosion is a type of intergranular corrosion and occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions, and high temperature. In general, this test method is more useful for stainless steels than the boiling magnesium chloride test of practice g36. Stress corrosion of type 304 stainless steel in chloride. Pdf stresscorrosion cracking behaviour of leanduplex. Stress corrosion cracking international institute of.

Stress corrosion cracking scc is the formation and growth of crack through materials subjected to tensile stress and a specific corrosive medium. Chloride stress corrosion cracking ssina specialty steel. This means that all environments do not cause scc on all of the alloys. The duplex stainless steels were developed to exhibit comparable general corrosion resistance as 316ss, but with reduced susceptibility to chloride stress corrosion cracking. The combination of tensile stress and a specific corrosive environment can crack stainless steels. Stress corrosion cracking sensitivity of supermartensitic stainless steels in high chloride concentration environment, proc conf corrosion 2004, usa, nace international, paper 04124. Effects of marine environments on stress corrosion.

Chloride scc is clearly the bane of austenitic stainless steels and one of the main reasons they are not the miraclecure for many corrosion problems. Stress corrosion cracking of an austenitic stainless steel in. Stress corrosion cracking scc 1 is a common and dangerous form of cracking that occurs due to the combination of stress and corrosive environments. Stress corrosion cracking scc is a common issue with many specialty alloys. Ricker, national institute of standards and technology stresscorrosion cracking scc is a term used to describe service failures in engineering materials that occur by slow, environmentally induced crack propagation. The limits for ldx 2101 duplex stainless steel application in h 2 scontaining environments the susceptibility to scc of ldx 2101 duplex stainless steel in the presence of cl. Behaviour of stress corrosion cracking of austenitic stainless. Stress corrosion cracking facts and how to reduce the risk. Deterioration by clscc can lead to failures that have the potential to release stored energy andor hazardous substances. There is a synergistic relationship between dissolved oxygen and the chloride level. Chloride stress corrosion cracking inspectioneering. A precursor of stress corrosion cracking in chloridebearing environments is pitting corrosion, occurring if the stainless steel is not sufficiently resistant to pitting. For example, chloride stress corrosion cracking of austenitic stainless steel has.

Scc is highly chemically specific in that certain alloys are likely to undergo scc only when exposed to a small number of chemical environments. For austenitic stainless steels chlorides are the major cause of stresscorrosion cracking scc. High performance stainless steels nickel institute. Scc is often associated with chlorides, but can also occur with caustics and other corrosive media. The benefits of n to scc resistance of dss are provided. Susceptible alloys include 304l, 316l, 321, and 347. Stainless steels types 304 and 316 can be considered resistant below 80 degc, up to the limit of solubility. These steels contain above approximately % cr and precipitate a prime phase in 350 o c to 540 o.

This mode of attack is termed stress corrosion cracking scc. The profound role of the environment chemistry in pittingcracking. Astm g123 002015 standard test method for evaluating. Previously, it was generally considered that an elevated temperature was necessary for scc to occur. Stress corrosion cracking of austenitic stainless steels. Corrosion resistance of ferritic stainless steels total. A material failure may be accelerated by the combined effect of corrosion and mechanical stress. The most common environmental exposure condition responsible for scc of stainless steels is the presence of chlorides. The influences of thermal treatment heat affected zone cases, composition, and microstructure on corrosion are given good coverage. An example is hot potable water under heat transfer conditions which permit chlorides to concentrate locally.

Ahmed and others published stress corrosion cracking of austenitic stainless steels in chloride environment find. Pitting corrosion of a stainless steel is illustrated in the figure 1. Effects of marine environments on stress corrosion cracking of austenitic stainless steels 1011820 effective december 6, 2006, this report has been made publicly available in accordance with section 734. Ferritic stainless steels have certain useful corrosion properties, such as resistance to chloride stresscorrosion cracking, corrosion in oxidizing aqueous media, oxidation at high temperatures and pitting and crevice corrosion in chloride media. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. Chloride stress corrosion cracking clscc is one the most common reasons why austenitic stainless steel pipework and vessels deteriorate in the chemical processing and petrochemical industries.