By applying the solution comprising 0.5 to 10 % by weight of an inorganic polysilazane having repeating units represented by the general formula below and soluble in a solvent and a catalyst such as 4,4'-trimethylenebis (1-methylpiperidine) etc. onto the surfaces of the bodies and wheels of automobiles, dentures, tombstones, the interior and exterior of a house, products used with water in toilets, kitchens, washrooms, bathtubs, etc., signboards, signs, plastic products, glass products, etc., a rigid and dense silica coating is formed to confer a long-durable hydrophilic effect and anti-fouling effect on the surfaces. The solvent is properly selected from mineral spirit, paraffin type solvents, aromatic solvents, alicyclic solvents and mixture thereof depending on the article being coated.