Corrosion Behavior of A588 Weathering Steel Coatings Applied by Thermal Spray Techniques in Industrial Atmospheres

A588 weathering steel is a high-strength, low-alloy material that is commonly used in construction due to its resistance to atmospheric corrosion. However, the exposure to industrial atmospheres containing pollutants and aggressive agents could cause corrosion in the steel, leading to a decrease in its mechanical properties and expected lifetime. To prevent or delay the corrosion process, different coating techniques could be implemented, including thermal spray techniques such as plasma spraying and flame spraying. This article aims to review the corrosion behavior of A588 weathering steel coatings applied by thermal spray techniques in industrial atmospheres.

Thermal spray techniques involve heating a material in a molten or semi-molten state and projecting it onto a substrate to form a coating. The most common thermal spray techniques are plasma spraying and flame spraying, which produce coatings with different microstructures and properties. Plasma spraying produces coatings with high porosity, but also high adhesion strength, while flame spraying produces coatings with low porosity but low adhesion strength. Both techniques have been used to apply coatings on A588 weathering steel, mainly using zinc or aluminum-based materials as sacrificial coatings.

Zinc coatings are commonly used as sacrificial coatings in atmospheric exposure conditions due to their high corrosion resistance and ability to form a protective layer on the steel surface. Zinc coatings applied by plasma spraying on A588 weathering steel have shown good corrosion resistance in marine and urban atmospheres, reducing the corrosion rate of the steel by more than 90% compared to uncoated steel. However, in industrial atmospheres containing high levels of sulfur dioxide, zinc coatings have shown a decreased performance due to the formation of zinc sulfate, which is more soluble and less protective than zinc oxide.

Aluminum coatings have also been used as sacrificial coatings on A588 weathering steel, providing excellent corrosion resistance in industrial and marine atmospheres. Aluminum coatings applied by plasma spraying on A588 steel have shown a reduction in the corrosion rate by more than 95%, with an estimated lifetime extension of 10-20 years. The protective mechanism of aluminum coatings is based on the formation of an aluminum oxide layer that acts as a barrier to the corrosive agents. However, aluminum coatings are not suitable for high-temperature applications due to the susceptibility of aluminum to oxidation at high temperatures.

Other thermal spray techniques, such as high-velocity oxy-fuel (HVOF) spraying and electric arc spraying, have also been used to apply coatings on A588 weathering steel. HVOF spraying produces dense coatings with high adhesion strength, which have shown good corrosion resistance in acidic and marine environments. An HVOF-sprayed nickel-aluminum bronze coating on A588 steel has shown a reduction in the corrosion rate of more than 90% in a marine environment, compared to uncoated steel. Electric arc spraying produces coatings with low porosity and high adhesion strength, but with lower thickness than plasma or flame spraying. Electric arc-sprayed zinc coatings on A588 steel have shown a reduction in the corrosion rate of up to 80% in an industrial environment.

In conclusion, thermal spray techniques provide a promising solution to prevent or delay the corrosion of A588 weathering steel in industrial atmospheres. The selection of the coating material and technique depends on the specific atmospheric conditions and expected lifetime of the steel structure. Zinc and aluminum coatings are common sacrificial coatings that have shown good corrosion resistance in different atmospheric conditions, with plasma spraying and HVOF spraying being the preferred techniques. Other thermal spray techniques, such as flame spraying and electric arc spraying, could also be used depending on the specific application requirements.