The corrosion protection of heavy duty structures for example bridges, pipes, oil tanks, towers, radio and TV masts, walkways and large scale manufacturing units in metallurgical, chemical, energy and other industries is a major concern. The safety of structures exposed to moist atmospheres and seawater like ships, offshore platforms, seaports is more challenging. In several cases the surface to be secured is excessively large needing that competitive coating with traditional painting. The coating rate should be minimum 10 m2/h and coating if possible should in deposited in single pass, the system should be mobile and autonomous for service in field conditions and can serve in manual control, automation being normally tough for large scale operations and the spray gun can be about 30 m away from other elements of systems. Coatings through thermal spray wire systems meet these needs. These systems are extensively used in industry as the economical and adherent solution without heating of the substrate.
The main application of thermal sprayed coatings is as sacrificial coating with standard thickness about 50 – 500 µm. These coatings offer cathodic behavior relatively to the ions of the metal to be secured in all steel cases. The cathodic protection can be porous without any attack on the base metal.
With wire arc spraying ,the atomization of the wire tips should be done with nitrogen to reduce the development of gamma TiO2.
Marine bio fouling is the unwanted accumulation of marine species on artificial surfaces that are immersed in the sea. When marine bio fouling occurs on the ship hulls, it can increase the ship weigh and sail friction. Here corrosion resistant alloys to sea water such as Monel 400 bar is used for better performance. Additionally monel wire is also used as coating material for sealers in these conditions.
Austenitic stainless steels, nickel base alloys containing chromium or nickel are used to prevent corrosion, usually when it is related with wear. Although such coatings without galvanic protection cannot protect the base material if connected porosities and oxide networks occur that happens in case of thermal sprayed coatings. So to protect substrate, a protective bond coat or dense coating or sealing are needed. Sealing is not possible in case of slightly higher temperature.
For oil and gas industry applications subjected to severe wear, the corrosion resistance of coatings can be enhanced by suitable choice of binder. The selection of materials for coating of valve components is an essential factor for economic success of oil and gas production processes in the petrochemical field. Particle erosion and surface wear are related to corrosion by hydrogen sulfide during oil and gas flow. For these applications, NiAl and composite material WC- intermetallic compounds containing Nickel, Chromium, Cobalt and Molybdenum are referred.
Corrosion resistant alloys find wide industrial use for offering high strength and corrosion resistant properties. For example Hastelloy C276 bar and Hastelloy C22 bar are widely used in chemical industries for offering excellent resistance to chemical media. Contact us to know more about these special materials.