Stress corrosion cracking of sensitized type 304 stainless. It has superior chloride stress corrosion cracking. It can be detrimental to austenitic stainless steels, one of the main reasons these steels are not considered a cureall for corrosion problems. The rate of stress corrosion cracking scc was measured for nonsensitized, coldworked type 316 uns s31600 and type 304 uns s30400 in both hydrogenated pressurized water. Deterioration by clscc can lead to failures that have the potential to release stored energy andor hazardous substances. Effects of marine environments on stress corrosion. It has superior chloride stress corrosion cracking resistance to types 304 and 316. The stress corrosion cracking scc of aisi 304 and aisi 316 austenitic stainless steels in 0. Specifications ak steel type 444 stainless steel sheet and strip is covered by the following specifications. Type 316 is an austenitic chromiumnickel stainless and heatresisting steel with superior corrosion resistance as compared to other chromiumnickel steels when exposed to.
It subjects to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60c. Chloride stress corrosion cracking in austenitic stainless steel is characterized by the multibranched lightning bolt transgranular crack pattern. Table 6 lists the relative corrosion resistance of the aisi standard numbered stainless steels in seven broad categories of corrosive environments. The major differences between 202 and 304 is the difference in their nickel and chromium content. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more saline or chlorideexposed environments. The combination of a duplex structure and high nitrogen content provide significantly higher strength levels than 316l stainless steel. Both aisi 316 vs 316l stainless steel are molybdenum mo containing austenitic stainless steel grades.
This diagram figure 1 is analogous to a similar diagram for caustic. Duplex alloys are more resistant to chloride stress corrosion cracking than types 304 and 316. Stainless steel 316 and 316l grade 316 is the standard molybdenumbearing grade, second inoverall volume production to 304 amongst the austenitic stainless steels. Again, 316ss is more resilient as it is less susceptible to corrosion from chlorine solutions than 304ss, which shows signs of corrosion at 2 ppm of chlorine and 316ss showing signs of. The 304 and 304l 188 stainless steel alloys have been utilized very successfully in fresh waters containing low levels of chloride ion of up to 100 ppm. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. Table 6 lists the relative corrosion resistance of the aisi standard numbered. Type 304 alloys are all modications of the 18% chromium, 8%. Chloride stress corrosion cracking cscc is a type of intergranular corrosion. What are the key features of stainless steel 202, 304, and.
It occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions and high temperature. Chloride stress corrosion cracking and 316 stainless steel. A precursor of stress corrosion cracking in chloride bearing environments is pitting corrosion, occurring if the stainless steel is not sufficiently resistant to pitting. Like 316, it is an austenitic stainless steel, meaning it is a metallic, iron allotrope. Molybdenum is a chemical element used for the strengthening and hardening of steel. The use of this stainless steel grade in chloride containing environments is not normally recommended. High performance stainless steels nickel institute. Oct 21, 2019 chloride stress corrosion cracking cscc is a type of intergranular corrosion. Stress corrosion cracking of aisi 304 and aisi 316 austenitic. 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. Chloride stress corrosion cracking scc of type 304 and 304l austenitic stainless steels ss was studied by a constant load method in air at a temperature of 353 k with relative humidity rh of. The combination of tensile stress and a specific corrosive environment can crack stainless steels. The stress corrosion cracking scc and hydrogen embrittlement he behaviors for types 304, 310, and 316 austenitic stainless steels were investigated in boiling saturated magnesium.
What is the difference between 304 and 316 stainless steel. Stainless 316 contains more nickel than stainless 304, while 304 contains more. Chloride stress corrosion involves selective attack of a metal along its grain boundaries. What differentiates 316 stainless steel from 304 stainless steel. The use of this stainless steel grade in chloride containing environments is not normally recommended unless they are carefully selected, their heat treatment is carefully specified. The stress corrosion cracking scc of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test. Hence the tendency for stress corrosion cracking of the plain 304 or 316 stainless steels in solution annealed condition is not considered to be different from its low carbon varieties.
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. The main difference between 304 and 316 stainless steel is 316 ss has the addition of molybdenum. The most common environmental exposure condition responsible for scc of stainless steels is the presence of chlorides. Corrosion of astm 304 grade stainless steel for drinking. Ak steel 444 is equivalent to type 304 in many corrosion environments and has lower coefficient of expansion and better thermal conductivity. After analyzing chemical composition makeup, corrosion resistance, cost and suitable applications, the key difference between 304 and 316 stainless steel is that 316 grade has better corrosion resistance thanks to addition of molybdenum than 304, especially for chloride applications, and last longer service life.
The material used in the present study is 304 stainless steel, the chemical composition of it is shown in table i. Alloy 304 stainless steel is considered to resist pitting and crevice corrosion in waters containing up to about 100 ppm chloride. Resistance to chloride stress corrosion cracking is correlated with nickel content, with the 25% nickel ss 904l alloy, showing improved resistance compared to an 8% nickel alloy like type 304 stainless steel. It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile. Chloride stress corrosion cracking in austenitic stainless steel is characterized. The differing chemical makeups of 304 ss and 316 ss influence how each performs in a certain environment.
This mode of attack is termed stress corrosion cracking scc. It is not as conductive, both electrically and thermally, as carbon steel and it is not magnetic. Chloride induced stress corrosion cracking in standard austenitic stainless steels, viz. Chloride stress corrosion cracking in austenitic stainless steel. Type 304 alloys are all modications of the 18% chromium, 8% nickel austenitic alloy. Aisi 316 vs 316l stainless steel, difference of ss316. Its main function in stainless 316 is to help fight off corrosion from chlorides. For example, chloride stress corrosion cracking of austenitic stainless steel has been experienced in hotwater jacketed pipes carrying molten chocolate in the food industry. Jan 08, 2002 while stainless steels are often used for their corrosion resistance, they do in fact suffer from corrosion under certain circumstances.
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. With respect to pitting and crevice corrosion resistance the high chromium. Stress corrosion cracking of aisi 304 and aisi 316. The main difference between 316 and 316l stainless steel is the level of carbon. After analyzing chemical composition makeup, corrosion resistance, cost and suitable applications, the key difference between 304 and 316 stainless steel is that 316 grade has. Well known stainless steel grade, very close to the 201 grade but with lower mechanical properties. The most essential characteristic of stainless steel is its corrosion. The mobearing alloy 316 and alloy 317l on the other hand will handle waters with up to about 2000 and 5000 ppm chloride, respectively. Type 304 stainless steel an overview sciencedirect topics. Type 304 and 316 since it is highly resistant to chloride stress corrosion cracking and is about twice as strong. Therefore, the scc concerns for spent fuel storage canisters identified in a november 2004 presentation by nuclear and. Often a lighter gage of ldx 2101 can be utilized to achieve the same strength levels of a 300 series fabrication. What is temperature it is more important than concentration of chloride and anything higher than room temperature higher is worse. It is difficult to control the temperature, while changing pipe material or eliminating residual stresses associated with welding and forming the pipework is costly and.
Molybdenum is a chemical element used for the strengthening and hardening of. Chloride stress corrosion cracking scc of type 304 and 304l austenitic stainless steels ss was studied by a constant load method in air at a temperature of 353 k with relative humidity. 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. I can only relate what i know about the specific corrosion of type 304 stainless steel used for valvepipe fittings in the nuclear pwr industry. Influence of high temperature on corrosion behavior of 304. Stress corrosion cracking of type 304 austenitic stainless. Resistance of the ss 904l alloy is further aided by presence of 4. Chloride induced stress corrosion cracking of type 304 and.
Stress corrosion cracking facts and how to reduce the risk. 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. At double eagle alloys, we have a wide range of type 316 and stainless super duplex type 2507 products in our inventory and the inhouse capabilities to customize our stock to you needs. Chloride stress corrosion cracking inspectioneering. This level of chloride is considered to be the limit for the 188 alloys, particularly if crevices are present. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more. The molybdenum gives 316 better overall corrosion resistant properties than grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. It is found that the stress vs timetofailure curves for both alloys are divided into three regions that. What is temperature it is more important than concentration of chloride and anything higher. Type 304, with its chromiumnickel content and low carbon, is the most versatile and widely used of the austenitic stainless steels. 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. Higher levels of chloride might cause crevice corrosion and pitting. Type 444 is equivalent to type 304 in many corrosion environments and has lower coefficient of expansion and better thermal conductivity. Pdf stress corrosion cracking of austenitic stainless.
Again, 316ss is more resilient as it is less susceptible to corrosion from chlorine solutions than 304ss, which shows signs of corrosion at 2 ppm of chlorine and 316ss showing signs of corrosion at 4 ppm of chlorine. 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. Chloride stress corrosion cracking and 316 stainless steel moltenmetal chemical 20 jul 11 07. The rate of stress corrosion cracking scc was measured for nonsensitized, coldworked type 316 uns s31600 and type 304 uns s30400 in both hydrogenated pressurized water reactor pwr primary. Mar 29, 2016 304 and its variant are general purpose stainless steel grade with good atmospheric corrosion resistance and many corrosive media. The most basic difference between the grades of steel is the presence of molybdenum in stainless 316. Effects of marine environments on stress corrosion cracking.
Sep 21, 2018 sae 304 stainless steel is probably the most common stainless steel alloy in use today. Alloys 316, 316l, and 317l are more resistant to atmospheric and other mild types of corrosion than the 188 stainless steel. The micrograph on the left x300 illustrates scc in a 316 stainless steel chemical processing piping system. Modes such as pitting, crevice, stress corrosion cracking, sulfide stress corrosion cracking, integranular, galvanic, contact, passivation and pickling are covered. The stress corrosion cracking scc of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test temperature under a constant applied stress condition in 0. Furthermore, he notes, the strength is needed to resist erosioncorrosion. Since duplex stainless steel alloys are stronger than the austenitic stainless steel, pumps cast of duplex stainless steel can be designed with thinner castings to reduce the components weight and cost while retaining its strength. Although no stainless steel grade is totally immune. Duplex stainless steel comparison to stainless steel 316l.
Aesthetically, there is no difference between the two. It is thought to start with chromium carbide deposits along grain boundaries that leave the metal open to corrosion. Chloride stress corrosion cracking in austenitic stainless. The primary concern in this case is for an insidious form of corrosion called chloride stress corrosion cracking, which gives little indication of crack initiation in very low halide levels, and in the. Resistance to chloride stress corrosion cracking is correlated with nickel content, with the 25% nickel ss 904l alloy, showing improved resistance compared. What are the effects of chlorides and fluorides on 316. The combination of a duplex structure and high nitrogen content provide significantly higher. The presence of 23 wt% molybdenum in the alloy makes the passive film stronger kain et al.