Metallizing, also referred to as thermal spray coating, is the process of applying a thin metallic coating to a substrate for the purpose of protecting it against corrosion and physical wear. Most commonly, aluminum, zinc and their alloys are used. These are heated either electronically or using a flame and are then sprayed onto a substrate that has already undergone some method of surface preparation.
Thermal spray coating is a viable method of corrosion protection for any metal or concrete surface that can be adequately blasted and cleaned before the application. Pure aluminum and zinc-aluminum alloy used via this method have been especially effective as marine coatings. Thermal spray coatings are often applied to bridges, locks and dams, piers, and other onshore and offshore facilities.
Thermal spray processing is a well-established means of forming coatings of thicknesses greater than about 50 μm, so-called thick coatings. A wide range of materials can be thermally sprayed for a variety of applications, ranging from gas turbine technology (heat engines) to the electronics industry. Thermal spray coatings have been produced for at least 40 years, but the last decade has seen a virtual revolution in the capability of the technology to produce truly high-performance coatings of a great range of materials on many different substrates. This enhancement of the technology has been achieved largely through the introduction of new spray techniques, the enhancement of spray process controls, the employment of state-of-the-art methods of feedstock materials production and the use of modern techniques of quality assurance. Thermal spraying has been present for over a century, being greatly refined, and optimized during this time. It has become nowadays a reliable and cost-efficient method to deposit thick coatings with a wide variety of feedstock materials and substrates. Thermal-sprayed coatings have been successfully applied in fields such as aerospace or electricity production, becoming an essential component of today’s industry.
Thermal spray coating refers to a number of processes in which a substrate is coated to improve functional performance. Many types of coating materials can be applied by thermal spray processes. Coatings can range in thickness from a thousandth of an inch up to an eighth of an inch. Thermal spray coatings have been used to protect parts from wear, abrasion, corrosion, high temperatures, etc. and to build dimensions on undersized parts.
The Process of Thermal Spray Coating
Thermal spray coating processes involve the deposition of coatings from a stream of high velocity finely divided particles in a molten or semi-molten state impinging onto the substrate. These processes use fine powdered source material or sometimes metal wire that is molten and broken into fine droplets. The coating gun adds thermal energy to bring the materials to a plastic or molten condition and accelerates these materials at high velocities toward the substrate.