The resistance of 316L to Cl- and F- corrosion?
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What is the resistance of 316L to Cl- and F- corrosion? There is a liquid medium containing 100–300 mg/m3 of Cl- and 100–300 mg/m3 of F-, at a temperature of 60 degrees. Will this medium cause severe corrosion to 316L?
316L is not resistant to chloride and fluoride ions; in an environment with Cl- levels of 100–300 mg/m3 and F- levels of 100–300 mg/m3, at a temperature of 60 degrees, corrosion occurs very rapidly. In such situations, nickel-based Hastelloy should be used
Chromium-nickel stainless steel is suitable for medium-temperature and medium-concentration alkaline solutions, such as those at 100 degrees Celsius with a concentration of less than 50%. As the temperature rises, corrosion increases; for example, when using stainless steel in evaporation tubes to concentrate alkaline solutions to 700 g/L, the maximum temperature can reach 150 degrees Celsius, and the lifespan of such materials is only three years. Chromium-nickel steel is also used in equipment for alkaline pulp processing, as well as in immersion tanks and mixers used in the production of viscose rayon. Chromium-nickel steel containing molybdenum, such as type 316, does not offer any advantages over stainless steel that lacks molybdenum. Chromium steel is only suitable for low-temperature, low-concentration alkaline solutions and can be used for storage tanks, but it is not as effective as chromium-nickel steel. Chromium-nickel stainless steel can be used in dilute sulfuric acid with a concentration of less than 5% and concentrated sulfuric acid with a concentration of over 90% at room temperature. Chromium-nickel steel containing molybdenum is more resistant to acid corrosion, but the operating temperature should not exceed 50–70 degrees Celsius. For sulfuric acids of moderate concentration and fuming sulfuric acid, all types of chromium-nickel stainless steel are highly susceptible to corrosion and are therefore not suitable for use. All chromium steels are not suitable for unfilled sulfuric acid at all concentrations. If other substances are present in sulfuric acid, such as chromic acid, sodium dichromate, sodium nitrate, and most sulfates, they have a corrosion-inhibiting effect on stainless steel.
Such a high concentration will certainly cause significant corrosion of 316L; in situations with tensile stress, it can lead to stress corrosion.
Austenitic stainless steels are sensitive to both CL- and F-, and are prone to stress corrosion cracking.
Are the units used by the poster for the chloride and fluoride concentrations incorrect? If not, then the concentrations are quite low; generally, these concentrations in water are below 25 PPm. 1 ppm equals 1 mg/L, so I suspect that the units are wrong; otherwise, using 316L material would be no problem.
Refer to the \"Corrosion Data and Material Selection Manual\" (compiled by Zuo Jingyi et al., Chemical Industry Press): Page 487: 316L, and the domestic grade Cr18Ni12Mo2~3. Due to the presence of Mo, these materials exhibit significantly improved resistance to corrosion by organic acids and chlorides compared to ordinary chromium-nickel stainless steels. P489: This type of stainless steel can be used in media containing 20–30% chlorides at temperatures below 80 degrees Celsius
Materials such as 316 are not resistant to CI ion corrosion.
Stainless steel is vulnerable to chloride ions; it’s best not to take the risk
The liquid medium contains 100–300 mg/m3 of Cl- and 100–300 mg/m3 of F-, at a temperature of 60 degrees; in other words, the levels of both Cl- and F- are below 3 PPM. Corrosion of 316L by this medium should not be severe, and it can withstand such conditions.