Analysis of the corrosion behavior of steel reinforcement protected by phosphate coatings

Abstract

The influence of phosphate coatings on the corrosion behavior of steel reinforcement in a chloride-containing environment was studied to determine the need for additional protection against corrosion. The main indicators of the corrosion rate of steel reinforcement with phosphate coatings in chloride-containing solutions were determined, confirming the high protective properties of these coatings. It was found that the corrosion rate of steel reinforcement protected by phosphate coatings is reduced by 3 times. The processes of electrochemical corrosion of steel reinforcement of strength class A500S from steel grade St3ps in concrete under the influence of aggressive environments containing chloride ions (2 % MgCl2 solution and HCl solution with pH = 5) were studied. The kinetics of the corrosion process of steel reinforcement with and without protective phosphate coatings in solutions of various compositions has been studied. The change in mass of steel reinforcement protected by phosphate coatings is 3-4 times less than that of samples without coating. The surface potential of steel reinforcement with phosphate films changes significantly more slowly than that of unprotected samples.

Production of Colored Phosphate Coatings on Steel

“…To obtain the color in the modified cold phosphating solutions the composition of which is given in Table 1 [16,20] chromium salts (for obtaining green coatings) and cobalt salts (for obtaining orange coatings) in an amount of 50 g/l, procyon olive green dye (for obtaining green coatings) and methylene blue and Prussian blue (for obtaining blue coatings) in an amount of 80 g/l were introduced.…”