Process for Forming Anticorrosive Coating

Abstract

Anticorrosive coating is formed cheaply and in a short period, which facilitates its general application to marine steel structures. A steel caisson 1 is used as a cathode, an undersea member 3 arranged in seawater and opposed to the steel caisson 1 is used as anode. Direct current is passed between the electrodes so that anticorrosive coating 8 is formed on the steel caisson 1 through electrolytic reaction of the seawater, thereby attaining anticorrosion. The electric current is passed between the electrodes such that coating 7 with magnesium hydrate as dominant constituent is formed on the steel caisson 1 to have a predetermined thickness; then, supply of the electric current is stopped. Thus, anticorrosive coating 8 is formed through compositional substitution effect of substituting calcium carbonate for the magnesium hydrate in the presence of seawater.

1 . A process for forming anticorrosive coating on a marine steel structure wherein the steel structure is used as a cathode, an anode being arranged in seawater to be opposed to said steel structure, direct current being passed between the electrodes, anticorrosive coating being formed on the steel structure through electrolytic reaction of the seawater, thereby attaining anticorrosion of the marine steel structure, characterized by passing the electric current between the electrodes so as to have current density to form coating having magnesium hydrate as dominant constituent on said marine steel structure, thereby forming the coating with a predetermined thickness, then stopping supply of the electric current to thereby provide anticorrosive coating through compositional substitution effect which occurs in the presence of the seawater to substitute calcium carbonate for the magnesium hydrate. 
     
     
         2 . A process for forming anticorrosive coating as claimed in  claim 1 , characterized in that the electric current is passed between the electrodes so as to attain current density of the marine steel structure in a range of 3 to 10 A/m 2 .