Abstract: A method of treating a corrosible steel substrate having a coating of oxidized steel thereon, which comprehends applying to the oxidized steel coating a solution of an alkyl silicate in quantity sufficient to saturate the oxidized steel coating, permitting the solution to cure by hydrolysis, and thereupon to apply a topcoating. The solution may be partially prehydrolyzed as within the range of 40-98% and may contain dry particulate matter which is water insoluble and having a coloration sufficient for visual detection so as to readily indicate the state of saturation of the oxidized steel coating. Furthermore, the solution may additionally contain water soluble corrosion inhibiting compounds for producing ions which will react with the anodic steel substrate.