What Does Chloride stress cracking (CISCC) Mean?
Chloride stress cracking is very common in chemical processing and petrochemical industries. It is considered the prime reason for the deterioration of austenitic stainless steel pipework and vessels used in the petrochemical industry. Damage caused by CI-SCC is easily recognizable from the highly branched cracks that look like spider webs or lightning-array type network visible on the material.
Cl-SCC has caused many pipeline failures and it continues to be a problem. This is primarily because of unanticipated contamination of equipment made with austenitic steel due to inadvertent chloride contamination. Design engineers should be aware of the potential consequences of using austenitic stainless steel where chlorides may be present. The high cost of replacing equipment can be economically devastating for some industries.
Austenitic stainless steel is an iron-based alloy that contains 19% chromium and 9% nickel. This steel is highly resistant to corrosion in most atmospheric and aqueous environments. However, wet and humid environments containing chloride ions can cause pitting and crevice corrosion of austenitic steel components. Furthermore, components that are under applied or residual stress can, under these conditions deteriorate further by stress corrosion cracking.
To reduce the risk of Cl-SCC, the plant and equipment design should be such that the concentration of mechanical tensile stress such as at sharp edges and notches is avoided. Proper material selection is also important though it is true that none of the stainless steel grades is completely resistant to chloride stress corrosion cracking.
Chloride stress cracking is also known as chloride stress corrosion cracking (CI-SCC).