Pitting corrosion is the most common type of corrosion when stainless steel is in direct contact with corrosive media, so it is also the most common type of corrosion in printing and dyeing machinery. It always starts with a small break in the passive film of stainless steel at temperatures above 100°C in the presence of chlorine. Once pitting corrosion is formed on the stainless steel surface, the contact between oxygen and metal is isolated, preventing the repassivation of chromium. The corrosion then spreads rapidly into the interior of the stainless steel, and the point slowly expands. If it is not controlled, it will evolve into general corrosion.
Pitting corrosion can occur on 316 stainless steel as long as up to 0.1 g/L NaCl is present at 130°C. At present, more industrial sodium chloride is still added in the dyeing process in China, which has become one of the important reasons for the short service life of printing and dyeing equipment. According to the author's visit, the service life of domestically purchased printing and dyeing equipment is generally 2-5 years (the core components are damaged), and the disparity is relatively large, which is mainly caused by the different use environments of the equipment.
