Protective Action of Phosphate and Calcium-Containing Pigments under the Conditions of the Stress Corrosion Fracture of Steels

We have established that strontium chromate and a mixture of modified zinc phosphate and calcium-containing pigment inhibit substantially the corrosion of low-carbon steel in slightly acid rain solution. We observed mainly the anodic control of corrosion in the extract of chromate pigment and mixed control in the extract of a mixture of nonchromate pigments. Zinc ions in corrosive media enhance significantly the protective action of this pigment mixture. Here, a crystal-like protective film, consisting of calcium and zinc phosphates, is formed on the surface of steel. The extracts of chromate pigment and a mixture of nonchromate pigments in a slightly acid medium increase the resistance of low-carbon steel to corrosion fatigue in the stages of crack initiation and growth. Thus, the necessary prerequisites are created for enhancing the service life of steel constructions with organic coatings, containing inhibiting pigments, under conditions of the joint action of a corrosive medium and cyclic loading.