Corrosion resistant coating and method for coating metal substrate

A method of protecting a metal substrate from corrosion comprising:

• applying to at least a portion of the surface of the substrate a thin and wet film of a liquid composition comprising powdered metal selected from the group consisting essentially of zinc, cadmium, stainless steel, aluminum, and alloys and blends thereof;
• said powdered metal having an average particle size not greater than about 40 microns and a maximum particle size not greater than about 100 microns;
• a resin system at least 80% by weight consisting essentially of a thermoplastic linear phenoxy resin having a high molecular weight in the range of about 3,000 to 60,000 and essentially no highly reactive terminal epoxy groups, the balance of said resin system consisting essentially of formaldehyde, melamine, phenolic, and triazine resins and blends thereof;
• the quantity of said resin system being about 10% to 525% by weight of said powdered metal;
• active organic solvent selected from the group consisting essentially of acetone, cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, and blends thereof;
• inactive organic solvent selected from the group consisting essentially of aromatic hydrocarbons, alcohols, and blends thereof in a quantity equal to about 0.1 to 0.4 by weight of said active organic solvent;
• the total quantity of said organic solvents being sufficient for the composition to have a viscosity in the range of about 20 to 280 seconds with a Ford No. 4 cup;
• and heating the thin wet film to an elevated temperature for a sufficient period of time to evaporate the solvents and thereby tenaciously adhere the film to the substrate as a coating protecting the substrate from corrosion without heating any portion of the substrate to a temperature greater than 450.degree. F.

The method of making a corrosion resistant coating for application to and curing at an elevated temperature on a metal substrate comprising:

• mixing together powdered metal having an average particle size not greater than about 40 microns and a maximum particle size not greater than about 100 microns, said powdered metal being selected from the group consisting essentially of zinc, cadmium, stainless steel, aluminum, and alloys and blends thereof;
• a resin system at least 80% by weight consisting essentially of a thermoplastic linear phenoxy resin having a high molecular weight in the range of about 3,000 to 60,000 and essentially no highly reactive terminal epoxy groups, the balance of said resin system consisting of formaldehyde, melamine, phenolic, and triazine resins and blends thereof;
• the quantity of said resin system being equal to about 10% to 525% by weight of said powdered metal, and a quantity of active solvent equal to about one to two times the weight of the linear phenoxy resin;
• agitating the mixture of powdered metal, linear phenoxy resin, and organic solvent, while elevating its temperature to 120.degree. F. to 180.degree. F.;
• milling the heated mixture to produce a homogeneous mixture having a Hegman grind rating in the range of 4.5 H to 7.5 H;
• and thereafter, blending the homogeneous mixture with a sufficient quantity of active and inactive organic solvents sufficient for the final blend to have a viscosity in the range of about 20 to 280 seconds with a Ford No. 4 cup;
• said active organic solvent being selected from the group consisting of acetone, cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide and blends thereof, and said inactive solvent being selected from the group consisting essentially of aromatic hydrocarbons, alcohols, and blends thereof in a quantity equal to about 0.1 to 0.4 by weight of said active organic solvent.