Abstract

The present invention provides methods for preparing or repairing a chemically-resistant coating such as a porcelain enamel on a metal substrate. One such method involves forming a ground coat on the substrate, cooling the substrate to substantially near ambient temperature, optionally by applying a heat source to cool the substrate slowly, followed by flame-spray depositing a coating material onto the softened ground coat. Then, the substrate is allowed to cool slowly so the chemically-resistant coating can form with less stress. Optionally, an induction coil is used to heat the substrate, both to form the ground coat and to slow the cooling of the substrate. Such methods allow for easier and faster repairs, and even in situ repairs of articles such as chemical reactor vessels, covers, baffles, thermowells, agitators, agitator shafts, pipes, heat exchangers, and storage tanks, as well as white goods such as ovens, stoves, washing machines, driers, in addition to bathtubs, sinks, and shower stalls, in addition to steel girders and steel reinforcing bars. Articles having a chemically-resistant coating also form a part of the invention.

IPC Classes  ?

• B05D 5/00 - Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
• B05D 3/02 - Pretreatment of surfaces to which liquids or other fluent materials are to be appliedAfter-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
• B05D 1/02 - Processes for applying liquids or other fluent materials performed by spraying
• C23C 4/12 - Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
• C23C 4/10 - Oxides, borides, carbides, nitrides or silicidesMixtures thereof
• C23C 4/18 - After-treatment
• C23C 4/02 - Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• C23D 3/00 - Chemical treatment of the metal surfaces prior to coating
• C23D 5/04 - Coating with enamels or vitreous layers by dry methods
• C23D 1/00 - Melting or fritting the enamelsApparatus or furnaces therefor

Abstract

The present invention provides methods for preparing or repairing a chemically-resistant coating such as a porcelain enamel on a metal substrate. One such method involves forming a softened ground coat on the substrate by heating to or maintaining an elevated temperature, followed by flame-spray depositing a coating material onto the softened ground coat. Then, the substrate is allowed to cool slowly so the chemically-resistant coating can form with less stress. Optionally, an induction coil is used to heat the substrate, both to form the softened ground coat and to slow the cooling of the substrate. Such methods allow for easier and faster repairs, and even in situ repairs of articles such as chemical reactor vessels, covers, baffles, thermowells, agitators, agitator shafts, pipes, heat exchangers, and storage tanks. Articles having a chemically-resistant coating also form a part of the invention.

IPC Classes  ?

• C23C 26/00 - Coating not provided for in groups
• C23C 30/00 - Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process