Testing of pigmented coatings on thermal sensitised stainless steel

Abstract

Purpose - The purpose of this paper is to verify the capability of pigmented coatings to mitigate the effects of thermal sensitisation of 430 stainless steel. Design/methodology/approach - Experimental weld joints of non-stabilised ferritic corrosion resistant steel type AISI 430 were prepared. Protective coatings in several variants were applied to a number of weldments, subsequently subject to corrosion tests in SO2 and NaCl. The anticorrosive efficiency of the coatings was evaluated by means of normative visual assessment and metallographic analysis of the mechanism and depth of corrosion damage. Findings - Anticorrosive efficiency of the tested coatings was experimentally established under conditions where differences were identified in structural changes caused by welding, or resulting from mechanical damage to the coating. Differences in the progress of corrosion damage caused by phase changes in the heat-affected zone were established. Practical implications - Tests of anticorrosive efficiency of coatings of selected types provided information about possible reduction in sensitisation of welded non-stabilised steel. The effect of the investigated processes on degradation of anticorrosive resistance was identified. Originality/value - A specific effect of phase changes accompanying welding on the corrosion mechanism was described and so were the reasons underlying development of corrosion damage at visually identical character of surface damage. Anglická klíčová slova: stainless steel; coatings; pigments; corrosion; destabilisation; welding; corrosion resistant ferritic steels; anticorrosive pigment; zinc; organic coating