The International Standard BS EN ISO 2063 as well as AS/NZ 2312 gives recommendations of coating thickness and time until first maintenance.
In North America, the Metal Spray process is known as “Metallizing” or “Thermal Spray”, with early work being carried out by the American Welding Society (AWS) who in 1953 exposed panels coated with flame sprayed zinc and aluminium and various sealers. Very favourable results were reported after 19, 34 and 44 years of exposure at coastal and industrial sites. This work was followed up by the US Army Corps of Engineers with successful trials of Metal Spray as a more abrasion resistant coating than vinyl on dam gates, and which resulted in a comprehensive design manual (USACE, 1999) which is available on the internet.
The US Federal Highway Agency noted (FHWA 1997) that work by the AWS and US Navy showed that “properly applied metallized coatings (zinc, 85% Zinc/15% Aluminium, and Aluminium) of at least 6 mils thickness provide at least 20 years of maintenance free corrosion protection in wet, salt-rich environments and are expected to provide 30 years of protection in most bridge exposure environments”. The FHWA has sponsored several research projects coating steel bridge beams with TSM, including one of environmentally acceptable materials which found that the thermal sprayed zinc (TSZ) systems were the best performing over 40 coating systems tested (which included top coated and single coat “high-ratio” and other inorganic zinc silicates) with no undercutting at scribe marks after 6.5 years exposure, and had the lowest life cycle cost.
Thermal Sprayed Aluminium (TSA) has been widely used in offshore oil and gas industry and by 1997 over 400,000 sq. metres of TSA had been applied to oil platforms in the North Sea to provide corrosion protection to flare stacks, riser pipes in the splash zone and submerged tethered legs (e.g. Conoco’s Hutton platform built in 1984). Experience indicated that TSA coatings, when properly applied and with the use of specific sealer systems, will provide a service life in excess of 30 years with zero maintenance required.
In short, the years of testing and results which have accumulated into the various standards demonstrate the coatings ability to withstand the harshest of environments and to with stand the test of time.
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Read more about environmental considerations in Is Metal Spray a Green process?