This level of chloride is considered to be the limit for the 188 alloys, particularly if crevices are present. The use of this stainless steel grade in chloride containing environments is not normally recommended. Stainless steel 316 and 316l grade 316 is the standard molybdenumbearing grade, second inoverall volume production to 304 amongst the austenitic stainless steels. The presence of 23 wt% molybdenum in the alloy makes the passive film stronger kain et al. The mobearing alloy 316 and alloy 317l on the other hand will handle waters with up to about 2000 and 5000 ppm chloride, respectively. The major differences between 202 and 304 is the difference in their nickel and chromium content. Chloridechlorine levels and stainless steel alloy selection.
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. The differing chemical makeups of 304 ss and 316 ss influence how each performs in a certain environment. A precursor of stress corrosion cracking in chloride bearing environments is pitting corrosion, occurring if the stainless steel is not sufficiently resistant to pitting. Although no stainless steel grade is totally immune. Chloride induced stress corrosion cracking of type 304 and. 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. Influence of high temperature on corrosion behavior of 304. Chloride stress corrosion cracking in austenitic stainless steel is characterized by the multibranched lightning bolt transgranular crack pattern. 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.
Molybdenum is a chemical element used for the strengthening and hardening of steel. Aisi 316 vs 316l stainless steel, difference of ss316. Chloride stress corrosion cracking and 316 stainless steel moltenmetal chemical 20 jul 11 07. Type 304, with its chromiumnickel content and low carbon, is the most versatile and widely used of the austenitic stainless steels.
The two most common stainless steel grades are 304 and 316. 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. Stress corrosion cracking of sensitized type 304 stainless. Type 304 and 316 since it is highly resistant to chloride stress corrosion cracking and is about twice as strong. Type 304 alloys are all modications of the 18% chromium, 8%. Table 6 lists the relative corrosion resistance of the aisi standard numbered stainless steels in seven broad categories of corrosive environments. Chloride stress corrosion cracking in austenitic stainless steel is characterized. The main difference between 304 and 316 stainless steel is 316 ss has the addition of molybdenum. Corrosion of astm 304 grade stainless steel for drinking.
Chloride stress corrosion cracking in austenitic stainless. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more. The material used in the present study is 304 stainless steel, the chemical composition of it is shown in table i. Resistance to chloride stress corrosion cracking is correlated with nickel content, with the 25% nickel ss 904l alloy, showing improved resistance compared. The stress corrosion cracking scc of aisi 304 and aisi 316 austenitic stainless steels in 0. Chloride stress corrosion involves selective attack of a metal along its grain boundaries. 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. Alloy 304 stainless steel is considered to resist pitting and crevice corrosion in waters containing up to about 100 ppm chloride. What differentiates 316 stainless steel from 304 stainless steel.
The micrograph on the left x300 illustrates scc in a 316 stainless steel chemical processing piping system. The combination of tensile stress and a specific corrosive environment can crack stainless steels. What is the difference between 304 and 316 stainless steel. It is found that the stress vs timetofailure curves for both alloys are divided into three regions that. Mar 29, 2016 304 and its variant are general purpose stainless steel grade with good atmospheric corrosion resistance and many corrosive media. This diagram figure 1 is analogous to a similar diagram for caustic. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more saline or chlorideexposed environments. With respect to pitting and crevice corrosion resistance the high chromium. Like 316, it is an austenitic stainless steel, meaning it is a metallic, iron allotrope.
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. The most basic difference between the grades of steel is the presence of molybdenum in stainless 316. 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. 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. 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. It occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions and high temperature. Duplex stainless steel comparison to stainless steel 316l. 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. 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. Chloride induced stress corrosion cracking in standard austenitic stainless steels, viz. Type 316 is an austenitic chromiumnickel stainless and heatresisting steel with superior corrosion resistance as compared to other chromiumnickel steels when exposed to. Deterioration by clscc can lead to failures that have the potential to release stored energy andor hazardous substances.
What is temperature it is more important than concentration of chloride and anything higher than room temperature higher is worse. Higher levels of chloride might cause crevice corrosion and pitting. Sep 21, 2018 sae 304 stainless steel is probably the most common stainless steel alloy in use today. What are the key features of stainless steel 202, 304, and. Ak steel 444 is equivalent to type 304 in many corrosion environments and has lower coefficient of expansion and better thermal conductivity. Stress corrosion cracking facts and how to reduce the risk. 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. Alloys 316, 316l, and 317l are more resistant to atmospheric and other mild types of corrosion than the 188 stainless steel.
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. It is thought to start with chromium carbide deposits along grain boundaries that leave the metal open to corrosion. Table 7 details more specific environments in which vari. For example, chloride stress corrosion cracking of austenitic stainless steel has been experienced in hotwater jacketed pipes carrying molten chocolate in the food industry. Modes such as pitting, crevice, stress corrosion cracking, sulfide stress corrosion cracking, integranular, galvanic, contact, passivation and pickling are covered. 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 inspectioneering. 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.
Type 304 stainless steel an overview sciencedirect topics. Duplex alloys are more resistant to chloride stress corrosion cracking than types 304 and 316. The combination of a duplex structure and high nitrogen content provide significantly higher strength levels than 316l stainless steel. 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. Type 444 is equivalent to type 304 in many corrosion environments and has lower coefficient of expansion and better thermal conductivity. Aesthetically, there is no difference between the two. Therefore, the scc concerns for spent fuel storage canisters identified in a november 2004 presentation by nuclear and. The molybdenum gives 316 better overall corrosion resistant properties than grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. It can be detrimental to austenitic stainless steels, one of the main reasons these steels are not considered a cureall for corrosion problems. 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. Type 304 alloys are all modications of the 18% chromium, 8% nickel austenitic alloy.
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. Stainless 316 contains more nickel than stainless 304, while 304 contains more. The stress corrosion cracking scc of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test. Oct 21, 2019 chloride stress corrosion cracking cscc is a type of intergranular corrosion. What is temperature it is more important than concentration of chloride and anything higher. 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. Jan 08, 2002 while stainless steels are often used for their corrosion resistance, they do in fact suffer from corrosion under certain circumstances.
It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile. 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. Pdf stress corrosion cracking of 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. The main difference between 316 and 316l stainless steel is the level of carbon. Stress corrosion cracking of type 304 austenitic stainless. Stress corrosion cracking of aisi 304 and aisi 316. High performance stainless steels nickel institute. Effects of marine environments on stress corrosion. This mode of attack is termed stress corrosion cracking scc. What is the maximum chloride in ppm that can be allowed in. 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. Resistance of the ss 904l alloy is further aided by presence of 4. Stress corrosion cracking of aisi 304 and aisi 316 austenitic.
Specifications ak steel type 444 stainless steel sheet and strip is covered by the following specifications. Table 6 lists the relative corrosion resistance of the aisi standard numbered. It has superior chloride stress corrosion cracking. 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 cscc is a type of intergranular corrosion. What are the effects of chlorides and fluorides on 316. It subjects to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60c. Its main function in stainless 316 is to help fight off corrosion from chlorides.
Molybdenum is a chemical element used for the strengthening and hardening of. It has superior chloride stress corrosion cracking resistance to types 304 and 316. It is not as conductive, both electrically and thermally, as carbon steel and it is not magnetic. Chloride stress corrosion cracking in austenitic stainless steel. The most common environmental exposure condition responsible for scc of stainless steels is the presence of chlorides. 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. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. The most essential characteristic of stainless steel is its corrosion. Furthermore, he notes, the strength is needed to resist erosioncorrosion. Chloride stress corrosion cracking and 316 stainless steel. 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. Well known stainless steel grade, very close to the 201 grade but with lower mechanical properties. The combination of a duplex structure and high nitrogen content provide significantly higher. Often a lighter gage of ldx 2101 can be utilized to achieve the same strength levels of a 300 series fabrication.