How Do Metal Spray Coatings Work?
Zinc Wire For Thermal Spray Metalizing

How Do Metal Spray Coatings Work?

As part of the development of metal science, it was identified that it was possible to provide additional protection to a metal by placing a layer of another less reactive metal on the surface. This could be protection from natural environmental factors (such as rust caused by oxidation), the operational environmental factors of industry such as chemicals or heat, the reduction of the impact of wear, or the provision of some level of thermal protection.

Previously a method had been developed for metal and steel fabrication where items were dipped in another substance that had been melted such as galvanising. There were two consequences of this. The substance they were to be dipped in usually had to be in a molten state, which meant there was the need to have large amounts of energy to keep that substance in a suitable state, as well as the associated safety hazards. The second issue was that this also involved a substantial transfer of heat from the molten substance to the item being treated. This massive heat transference could cause warping and misshaping.

An alternative approach for metal and steel fabrication was needed that would offer protection, but at the same time would take away these problems. A simple and highly effective engineering solution was the development of a process known as thermal or metal spraying.

Thermal Spraying

Thermal spraying involves a process where a small amount of a substance, usually a metal, is melted and then sprayed onto another substance. The projection of these molten particles needs to be onto a suitably prepared surface where they will adhere and cool. These droplets will flatten out to form a solid layer. This layer can then be built up with additional spraying.

The amount of heat in the spray is relatively limited when this is compared to the size of the item being sprayed so that there is very little heat transferred to the item. This takes away the problem of any malformation being caused by heat transfer.

Metal or thermal spraying will be used on items that need protection from corrosion. It is able to be done in a range of environments and does not necessarily require heavy equipment. It provides suitable protection and will increase the life of the component being sprayed. Zinc coating is currently being used for wind turbine towers to reduce corrosion. Zinc coatings are still highly effective in protecting ferrous metals from rust in a number of other areas, including fishing boats and construction. Other examples of the use of metal spraying are a metal pedestrian footbridge and metal piping being sprayed with aluminium.

How the spraying process works

The spraying process occurs with the use of a flame spray where a flame heats the metal to a suitable temperature before spraying; arc spray which uses electricity to achieve the same result; plasma spray which uses gas heated by electricity to heat and spray the metal product; and high velocity oxygen fuel which uses a burning hydrocarbon fuel with oxygen to produce the heat to melt the metal and to then spray it on the workpiece.

There are different metals that are able to be used to provide suitable protection for the environment and also depending on what material the component is made from, with zinc and aluminium being two of the major products.

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The process is now commonly used by metal and steel fabrication operations, such as Spray Metal Engineering, for equipment in the construction sector, as well as marine, petrochemical, and some manufacturing environments. Contact us today for more information.