CORROSION RESISTANCE AND ANTI-CORROSION CHARACTERISTICS OF INTERFACE BETWEEN Al-5Mg THERMAL SPRAYED COATING AND HEAVY DUTY PAINT COATING IN AIRBORNE SEA SALT ENVIRONMENT

Abstract

 The objective of this study is to clarify corrosion resistance and anti-corrosion characteristics of the interface between Al-5Mg thermal sprayed coating and heavy duty paint coating in airborne sea salt environment. Atmospheric exposure tests were carried out in highly corrosive atmospheric environments with and without the effect of rainfall washing-off on adhered airborne sea salt. A strip-shaped coating defect was introduced into each specimen, and at the defect area the steel substrate was exposed to the atmosphere. After the exposure tests, the coating blister scans and AC impedance measurements were performed on specimens, while the elemental analyses using SEM-EDX, EPMA, etc. were also conducted. The results indicate that the deterioration occurred from the steel base-exposed portion with the corrosion resistance reduction in the overlapping layer, which deteriorated earlier than that in the single sprayed coating regardless of the atmospheric environment of the exposure sites. Besides, comparing to an airborne salt deposit environment with rain-washing effect, it was clear that this tendency would be more evident in an environment without rain-washing effect.