Effect of Adhesion and Corrosion Performance of Geomet 321 (Basecoat) and ML Black (Topcoat) Applications on Cataphoresis Coating

Abstract

The primary objective of the research was to improve the corrosion resistance and adhesion properties of metallic materials commonly used in the automotive industry. In order to achieve a higher level of corrosion protection, a combination of Cataphoretic and Geomet coatings has been applied. The first stage involved applying a cataphoretic coating and then improving the corrosion properties by sequentially applying Geomet 321 (second layer) and ML Black (third layer) over the cataphoretic base. The evaluation included the influence of sandblasting pre-treatment and various post-cataphoresis curing temperatures (ranging from 150 to 230 °C), focusing on their effect on both adhesion and corrosion properties. The results of the corrosion tests were classified into different categories: adhesion, water resistance, moisture resistance, salt resistance and cyclic tests. According to these results showed that the most favourable corrosion resistance was achieved by a three-layer coating approach (Cataphoresis+ Geomet 321+ Geomet ML Black), combined with sandblasting preparation and curing at 210 °C. It has been shown that the corrosion properties of two- and three-layer coatings improve depending on both the sandblasting pre-treatment and the curing temperature after cataphoresis.