ZINC
	METALLIZING For superior corrosion resistance

	Metallizing is the process of spraying molten metal onto a surface to form a coating. At Rainbow Paint & Blasting, we are using pure zinc wire which is passed through a specialized spray gun. The gun produces a flame that melts the wire as it moves through. The molten zinc is sprayed with compressed air onto the surface that is being coated. The zinc metal is anodic to iron and steel, thus it provides cathodic protection to the metal parts. Zinc provides galvanic protection to steel when it is subject to a corrosive environment, if a break occurs in the protective coating, the zinc is self-sacrificing, it will corrode rather than the steel.¹ To afford the maximum corrosion protection we recommend that the parts are first white-blasted to NACE1 (National Association of Corrosion Engineers) standard. This standard provides a clean, corrosion free base to receive the zinc spray, and a final topcoat of paint, or powdercoat. Blasting also provides a firmer grip for the coatings by creating a coarser surface. The standard reads as follows.
		NACE 1 White Metal Blast Cleaning - Removal of all mill scale, rust, rust scale, paint or foreign matter by the use of abrasives propelled through nozzles or by centrifugal wheels. A White Metal Blast Cleaned Surface Finish is defined as a surface with a gray-white, uniform metallic color, slightly roughened to form a suitable anchor pattern for coatings. The surface, when viewed without magnification, shall be free of all oil, grease, dirt, visible mill scale, rust, corrosion products, oxides, paint, or any other foreign matter.
	Metallizing alone provides substantial corrosion protection, however a duplex coating system (metal sprayed coating and sealing and/or painting) has a longer service life than the sum of the service lives of the metal coating and the paint system considered separately. The service life of the paint system is several times greater than when not applied to an anticorrosive metallized coating.² Painting and powdercoating also provide a much more attractive finished product than does metallizing alone. The following excerpt from The "Salt River Project Report," (1995) demonstrates the kind of results that have been achieved with metallizing.
		"An obvious part of the evaluation of the zinc metal spray on the 50' x 50' Fixed Wheel Gates of the Mormon Flat Dam was an estimate of the remaining service life. After twenty years of service, the coating was in excellent condition. Considering the material involved, the fact that there is no cure mechanism and the complete success of the application after two decades of very rigorous service preparing a realistic service life estimate was extremely difficult. The problem was approached backwards." "In spite of the excellent condition of the zinc metal spray, it was decided to assume that somewhere between 10 and 20 per cent of the useful life of the coating system had passed. When these percentages are applied to the actual twenty year life, an estimated service life of between 100 and 200 years is calculated! With zero maintenance."
	¹ Roads & Bridges, August 1986, page 23 ² ISO 2063, Annex B, Section B.3

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