Autodeposition is a waterborne process which depends on chemical reactions to achieve depositions. This process has been in commercial use since 1975. Since then, autodeposiiton has grown and matured. Since its inception, this unique process has been employed to coat over one billion square feet of surface. Presently, there are numerous installations in operation, coating a variety of fabricated steel parts forts for the automotive and general industry markets.

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An Autodeposition bath consists on a mildly acidic latex emulsion polymer, DI water and other proprietary ingredients. The bath solids are normally between 3% and 5% by weight. The bath viscosity is close to that of water with little or no organic solvents in the coating bath. Another characteristic of the autodeposiiton bath is its acidic nature; the pH is typically between 2.5 to 3.0 The autodeposition coating process is quite simple. The mildly acid batch liberates a small amount of iron from the steel parts being immersed, causing an immediate surface reaction that releases iron ions. These ions interact with the latex in solution causing coating deposition on the surface of the steel parts. The newly deposited organic film is adherent yet quite porous. This allows the chemical activators to diffuse rapidly in the film and reach the surface of the metal. The continuous formation of coating provides a film with a high degree of surface protection and corrosion resistance.

The coating thickness of the autodeposited film is time and temperature related. The film thickness continues to grow as long as ionic species are being produced at the coating / metal interface. Initially, the deposition process is quite rapid, but slows down as the film increases in thickness. Typically, film thickness is controlled from 0.6 to 1.0 mil.

A unique feature of the autodeposition process is the formation of a very uniform film over the entire surface of the workpiece, even in difficult-to-reach areas. This allows the coating dispersion to flow into and around the most complex shapes. Unlike coating, processes that require a charge to deposit the coating (i.e. where electrical energy is required to `throw\' the coating into recessed areas) autodeposition will coat tubular, assembled, or intricate-design areas uniformly. Autodeposition coating film thickness is controlled by diffusion of reactants in the bath and through the coating already formed on the surface of the substrate. The diffusion controls leads to a uniform coating thickness on complex shapes and in recessed areas.

It should also be mentioned that the autodeposition process does not require a chemical conversion coating stage or, in the case of an autodeposition process using Autophoretic 800 Series coating chemicals, even a heavy metal final rinse stage. The elimination of these stages leads to conside