AN EVALUATION OF METHACRYLIC ACID-MODIFIED POLY(ETHYLENE) COATINGS APPLIED BY FLAME SPRAY TECHNOLOGY

Using a flame spray coating process, the methacrylic acid-modified pol y(ethylene) copolymer was overlaid onto cold rolled steel surfaces. An appropriate setting of the rate of air flow led to the incorporation of increased numbers of functional oxygen derivatives, such as COOH an d C=O groups, into the copolymer. The interaction between these functi onal groups and the steel surfaces improved the interfacial bond stren gth of the copolymer-to-steel joints. However, such bond structures we re vulnerable to high pH, created by the cathodic reaction, H2O + 1/2O (2) + 2e(-) --> 2OH(-), at the corrosion side of a defect in the coati ng film. The attack of the alkali solution on the interfacial reaction products caused bond breakage in copolymer-steel linkages, thereby re sulting in cathodic delamination of the coating film from the steel. N evertheless, a low rate of delamination corresponded to a strong bond strength at the copolymer-to-steel joints.