Corrosion Resistance of Unlacquered Chromium-Plated Steel Sheets – Study on the Influence of Pickling and Chemical Treatment Steps of the Production Process

The corrosion resistance of chromium-plated steel sheets produced on an industrial scale was investigated. Two parameters of the production process were considered: pickling and chemical treatment. The specimens were produced at the industrial plant considering two different pickling conditions and two different chemical treatments: non-electrolytic and electrolytic pickling and non-electrolytic and electrolytic passivation respectively. Accelerated corrosion tests in the humid chamber, microscopy analyses, analyses of roughness and content of trivalent chromium in the passivation film and analyses of the content of metallic chromium in the coating by coulometry technique were performed. The results showed a low corrosion resistance of the materials produced with the non-electrolytic passivation, regardless of the pickling condition. The highest degree of protection of the base steel was achieved for the specimen produced by using the electrolytic route for both pickling and chemical treatment steps. This condition produced a mass of trivalent chromium in the passivation film greater than 8.0 mg∙m^-2, which provided an effective performance of the chromium-plated steel sheet.

Keywords:
Corrosion Resistance; Unlacquered Chromium-Plated Steel; Pickling; Chemical Treatment