March 15th, 2021
Thermal Spray Aluminum (TSA) is a durable coating capable of providing complete corrosion protection and significant lifetime improvement for equipment. Thermal spraying techniques provide a versatile and cost-effective way of imparting high-performance coatings, lending thermal spray aluminum to a huge range of industrial and infrastructure applications.
Properties of Thermal Spray Aluminum
Thermal spray aluminum coatings are commonly applied in marine, pipeline and offshore infrastructure applications, especially where structures and components are exposed to seawater. In these applications, coating steels with thermal spray aluminum protects them against corrosion by setting up a cathodic circuit: the difference in electrochemical potential between steel and aluminum means that the steel effectively becomes a positive electrode (cathode) of a cell while the aluminum coating acts as a negative electrode (anode). The circuit is completed by water, and the resulting electrochemical action means that the aluminum corrodes preferentially to the steel, acting as a ‘sacrificial’ material and protecting the steel structure.
Thermal spray aluminum also imparts resistance to erosion and other types of mechanical wear. Additional benefits of aluminum include relatively low cost and high operating temperature (up to 538°C).
Thermal Spraying Fundamentals
The term “thermal spraying” denotes a group of distinct techniques, all of which involve heating a feedstock material (usually in powder or wire form) and propelling it towards a target substrate. The spray of melted or partially-melted feedstock material forms lamellae or “splats” on the target, which build up to create a uniform coating.
Thermal spray aluminum most commonly uses wire arc spraying or flame spraying. Both of these methods use aluminum wire as a feedstock, which is heated above melting point and sprayed across a surface by a jet of compressed air or inert gas. The primary difference between these two methods is the means of supplying energy to the aluminum wire: wire arc spraying uses an electric arc to melt the aluminum, while combustion wire spraying uses an oxy-fuel flame. As the name suggests, wire arc spraying uses a wire feedstock, which is much more economical than coating with powder – particularly for large area substrates.
While arc spraying achieves higher throughput of wire, flame-spray has a higher build-rate for its lower throughput, evening out the final coating rate. Flame spray torched also lead to higher, less-oxidized coating quality and a more controlled spray pattern with less fumes and need for PPEs.
Applications of Thermal Spray Aluminum
Thermal spray aluminum is a simple, versatile and cost-effective coating. Its anti-corrosive properties lend it to widespread use in coating bridges, ship decks, large metal tanks, and other metal structural components that would be otherwise susceptible to corrosion.
Saint-Gobain provides a complete range of flame spray coating technologies and metallic and ceramic materials, including aluminum wire feedstocks for thermal spraying applications. Contact a member of the team today if you would like to learn more.