INVESTIGATION OF TRIVALENT CHROMIUM-BASED CONVERSION COATINGS ON ELECTROGALVANISED STEEL

Abstract

The passivation process of electrogavanised steel is very important, especially for improving of the corrosion protection and the thickness of the layer obtained can further enhance such protection. In the market exists Cr(III)‑based thick layers passivation, however, are operated around 60°C. In order to attend market demands a new process with only 20% of the chromium content is developed, which operates at room temperature. The corrosion behavior was investigated through electrochemical impedance spectroscopy technique in chloride solution and accelerated tests in salt spray chamber. The combination of these tests provides a more complete assessment of the behavior against corrosion of layer passivation obtained. The results with respect to appearance, brightness, uniformity, layer thickness and corrosion resistance are similar to those presented by Cr(III) based passivation existing market and Cr(VI) based conversion treatment.

Keywords

• Corrosion; Electrogalvanised steel; Trivalent chromium.