Electrocleaning of Cold Rolled Steel Sheets

Abstract

Electrodegreasing of cold rolled steel sheets in an alkaline solution containing silicate was investigated by surface sensitive techniques. The influence of the contamination levels of the sheets and the solutions was studied. A model for the electrodegreasing mechanism is given: desorption of hydrocarbons from the surface occurs at polarization of the surface; readsorption is prevented by formation of microemulsions in the solution. Anodic electrocleaning gives a more efficient cleaning than cathodic degreasing. It is suggested that the number of bonds is reduced and the desorption from the surface is facilitated by oxidation of double bonds in the hydrocarbons adsorbed on the surface of the anode. Sodium silicate, Na2SiO2(OH)2, is deposited on the surface during electrodegreasing. More silicate is found after cathodic polarization than after anodic polarization. The precipitation at the cathode is explained by an increase in the pH value at the surface.