• Corrosion Science and Technology
• /
• v.12 no.5
• /
• pp.203-208
• /
• 2013

The electrocoating for automotive bodies is pigmented with a mixture of titanium dioxide and kaolin. In this study, the effects of titanium dioxide and kaolin contents in coating on electrodeposition process, drying, and surface properties such as surface roughness, gloss, impact resistance and corrosion resistance were investigated. Titanium dioxide and kaolin in coating do not have a decisive effect on curing reaction during drying and corrosion resistance but on gloss, surface roughness, impact resistance and electrodeposition process of coating. According to its size and shape on coating surface, pigment contents increased during drying process. However, the contents of kaolin and $TiO_2$ in coating didn't affect the corrosion resistance on zinc phosphated substrate, and the curing properties.

• Corrosion Science and Technology
• /
• v.12 no.5
• /
• pp.253-258
• /
• 2013

Effects of copper hydroxide(II) on the curing and the corrosion resistance of electrocoating were investigated by MEK rubbing test, electrochemical impedance spectroscopy (EIS) and Thermo-gravimetric analysis (TGA). Curing performance of electrocoating was lowered with increasing the content of copper hydroxide(II) as evidenced by the MEK rub performance which decreased with increasing the content of copper hydroxide(II). This indicates copper hydroxide(II) affected the blocked isocyanate reaction in the coatings, by the decomposition of copper hydroxide(II) to CuO and $H_2O$ during reaction of isocyanate with nuclephiles. Corrosion resistance of coatings also decreased with the content of copper hydroxide. This reflects the higher barrier property in coatings with higher curing performance.

• Corrosion Science and Technology
• /
• v.12 no.6
• /
• pp.288-294
• /
• 2013

When the automotive body enters an electrocoating tank while applying an electric current, its steel surface is exposed to a very low induced current. Consequently, surface defects of coating may arise if the steel surface has lack of electric uniformity due to local defects such as local oxide. In this study, we investigated the preceding assessment methods to evaluate steel susceptibility of the low induced current during electrocoating before mass production. Prior to general electrocoating, we applied low constant voltage such as 3V or low constant current densities such as $0.35mA/cm^2$ and $0.50mA/cm^2$. In result, we confirmed that such methods were efficient for assessing steel susceptibility of low induce current during electrocoating.