Gradual chemical or electro-chemical attack by atmospheric contaminants, moisture or other agents. It occurs in many forms, such as general pitting, and crevice and intergranular corrosion. It is evidenced most obviously as rust on steels or pits on aluminum. See STRESS-CORROSION CRACKING.
Causes: Wrong type of electrode diminishes corrosion resistance of the weld as compared to the parent metal; improper weld deposit for the corrosive media; the metallurgical effect of welding; and improper cleaning of the weld.
Corrections: Proper use of electrodes that provide equal or better corrosion resistance than the parent metal. When welding 18-8 austenitic stainless steel, the analysis of the steel and the welding procedure should be correct to avoid carbide precipitation: this condition can be corrected by annealing at 1040 to 1150°C (1900 to 2100°F).
