BOROSILICATE COATINGS ON MILD-STEEL PREPARED FROM AQUEOUS AMINE SOLUTIONS - A COMPARISON WITH THE ALKOXIDE ROUTES

Sol-gel coatings on metals, as barriers against oxidation of the subst rate may be obtained by the dip-coating technique. Different alkoxide solutions have been previously used to deposit coating films on variou s metallic substrates. Borosilicate coatings gave a good protection ag ainst the oxidation of mild steel. The preparation of these coatings h as however some disadvantages, such as the required low humidity durin g deposition and the high cost of precursors. In this work we studied an alternative method based on aqueous amine solutions. The borosilica te solutions prepared by amines and by alkoxides were characterized by measuring viscosity and stability. Coatings were deposited on mild st eel by both methods. Samples were treated at 550 degrees C and the oxi dation was evaluated by glancing angle X-ray diffraction. Adhesion tes ts and microscopic observations were performed to compare the behavior of amine- and alkoxide-derived borosilicate coating films.