Chromium martensitic stainless steel and ferritic stainless steel according to different conditions can cause stress corrosion cracking (mainly intergranular cracking) or hydrogen embrittlement, but this kind of stainless steel in MgCI2 or NaCI solution, resisting performance is far stronger than austenitic stainless steel, and under the condition of load stress is not strong, will not cause cracking.
The austenitic stainless steel is liable to crack in high temperature environment containing chloride aqueous solution. In the cooling water, the water vapor in the CI – probably in more than 50 PPM, temperature in the case of more than 50 ℃ about likely to happen, there are in many cases, the dissolved oxygen in a few parts per million of C1 – concentration will also form the corrosion cracking. It is more likely to cause corrosion cracking near the boiling point or boiling point of the solution, and sometimes in a very short time.
304 stainless steel has cracking sensitivity in high temperature and high pressure water. The austenitic stainless steel in MgCI2 solution will be affected by stress corrosion cracking. 1 nacl concentration and dissolved oxygen on the influence of the stress corrosion cracking of stainless steel 304 (temperature at 260 ℃, load stress is 21000 psi) is one of the important influencing factors as related to stress corrosion cracking, in addition to stress) chloride concentration, temperature, degree of processing also leads to great impact.
Temperature rise can cause stress corrosion cracking in stainless steel, and the influence size of stainless steel is also changed according to the type of alloy and the residues stress. In terms of degree of stainless steel processing, usually in the range of is not how big along with the deepening degree of stainless and much easier to crack, but it is important to note when processing degree of more than 10%, stainless steel materials will be difficult to crack.
Pitting corrosion is in the case of stainless steel passivation membrane stability, when the solution PH value near the neutral, antioxidants and halogen ions, C1 – in particular, passivation membrane will be destroyed by part forming cell anode, because of the passivation membrane as cathode, making this area form a larger potential difference, and in a short period of time the phenomenon of erosion depth stainless steel.
In order to avoid corrosion of stainless steel, there are mainly electrical and anti-corrosion, adding preservatives, surface spraying, controlling PH value, removing oxidant, etc. The surface treatment of stainless steel is also best to do some work on the residual stress of the surface, so that the stress can be compressed.
Source: China Stainless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)