The complete discaling before painting may be the only appropriate method for preventing pitting resulting from electrochemical action. The surface of long steel pile, steel sheetpile or other steel materials used in harbors is normally treated by sandblasting or wire brushing, while in the catalog, the steel piece with clean surface is generally shown.
　The auther wondered if the surface condition of steel might affect the effect of coating. So, to make protective effect of coating under practical condition clearer, the relation between several typical coatings and steel surface preparations was quantitatively tested in field.
　As a result, it is confirmed that the estimation of protective effect of certain coating should be done based on the result of the test carried out with the steel specimen of similar surface condition to that of steel material to be used in harbors.