Process

Metallizing is a versatile process which melts zinc or zinc alloy metals, and then rapidly propels the molten zinc particles onto a prepared substrate, creating a layered coating.  Also referred to as thermal spraying, it is a highly effective and proven method of corrosion protection, giving galvanic as well as barrier coating protection to iron and steel.

Properties

Most protective coating systems for steel function solely by acting as a barrier between the steel and the corrosive environment.  If these passive and permeable barriers are damaged or penetrated, moisture and oxygen can reach the steel causing rust and eventually coating failure.  A zinc metallized coating also offers barrier protection; however, the electrochemical relationship between zinc and steel allows a zinc coating to give cathodic protection as well.  A zinc metallized coating will protect the steel galvanically: it will corrode in preference to steel, continuing to protect as long as any zinc remains in the immediate area.

The surface of a metallized coating permits excellent adhesion of sealers and topcoats.  The effect of this combination is a synergistic coating system which will protect the underlying steel and require little or no maintenance for many years.

Application

Before application begins, the steel substrate must be sandblasted to remove all paint, rust and millscale and to provide an anchor profile that permits a sound mechanical bond with the alloy metal.

There are two types of equipment, both used by Daam, to spray metallize.  A gas flame gun uses a combustible gas to melt a single wire and then compressed air blows the atomized particles onto the steels surface.  The slower of the two types, this equipment is typically used to repair damaged galvanized coatings and coat small jobs where overspray is a concern.  The second type is Arc-Spray, where two electrically charged wires are fed simultaneously into an arc which melts the zinc and compressed air blows the particles onto the steels surface.  An arc spray gun is typically used for large jobs which require a large amount of zinc deposited at a rapid rate to meet delivery commitments.

Any thickness of coating can be specified, with the typical range falling between 100 - 300 microns (4 - 12 mils).  Depending on the atmospheric conditions, and coating life requirements the specified coating thickness can be increased accordingly.  In addition, edge protection is effectively achieved with metallizing.  Finally, as an additional measure a synergistic coating can be realized by adding a sealer and/or top coat of urethane or epoxy.

Advantages

There are 5 advantages to using metallizing: