Abstract: Disclosed is a single-application non-electrolytic method for the treatment of bare metal surfaces to form a corrosion-resistant coating. The clean metal surfaces are treated with an aqueous composition containing a melamine-formaldehyde resin and a vegetable tannin. The resulting dried coating exhibits superior qualities for a single-application coating process when used as a paint base and the process does not require the use of environmentally objectionable chromium compounds. Application to ferrous, zinc or aluminum surfaces may be by any known technique designed to provide a deposited layer of desired uniformity.

Abstract: Disclosed is a process for the post-treatment of conversion-coated metal surfaces. The aqueous treating solution contains a melamine-formaldehyde resin and preferably contains a vegetable tannin and is free of chromium. Treatment with the melamine-formaldehyde resin-containing solution provides improved corrosion-resistance over that obtained with a water rinse and treatment with the melamine-formaldehyde resin and vegetable tannin combination solution gives corrosion results as measured by salt spray resistance comparable to those obtained with the use of the commercial dilute chromium-containing rinse.

Abstract: Disclosed is a process for applying a tannin containing post-treatment composition over zinc phosphate conversion coatings on metallic surfaces so as to provide an improved base for paint, lacquer, varnish, or similar organic finishes. Also disclosed are a process for the transport and application of the tannin composition and a process for preparing a metallic surface for electrodeposition painting.