Thermal Spray Corrosion Resistant Coatings
Thermal spray corrosion resistant coatings are excellent coating barriers for corrosion protection. Oftentimes, their greatest benefits are derived under higher temperatures or mechanical wear, beyond thresholds afforded by plastics.
Of course, these materials can be built to significant levels, 0.010 inch, 0.020 inch or more. Which can be a great advantage in certain atmospheric or chemical corrosion environments. In applications requiring corrosion resistance, more is often better. Their ability to create pin hole free surfaces, absence of microscopic coating voids, is high.
Conversely, for dynamic applications also requiring low friction, post finishing will probably be necessary. Surface finishes in their ‘raw’ form are often 300 micro inch, or more.
Disadvantages include the fact that this technology is applied ‘line of sight’. So coverage will be limited to external surfaces, relatively simple geometry, and internal surfaces considered highly accessible.
Typical coating builds start at 0.003 to 0.005 inch, per surface. To allow for post finishing, where a fine micro finish is required, consider an allowance for machining, extra coating stock of 0.010 inch or more.
Whether your corrosion is general atmospheric or ambient oxidation, or hostile chemical corrosion, thermal spray corrosion resistant coatings can offer enormous advantage. Especially in dynamic environments involving moving parts, or extreme temperature, or both.
Many products today are regarded non-objectionable with the Food & Drug Administration (FDA), based on their low likelihood of migrating into food product in any measurable amount.
Depending on the mechanics of the environment, HVOF (high velocity oxygen flame) may be ideal for its increased density, stronger bonds and lower residual tensile stress.
Compared with other combustion powder thermal spray process (LVOF), plasma spray or vacuum arc spray, which are also popular.
Remember, besides material selection from your thermal spray corrosion resistant coatings, the key to sustainable corrosion protection is lower surface porosity, perfect isolation of the base metal. Any exposed metal prone to corrosive attack will disassociate from the parent metal, taking the coating with it!
While there are emerging technologies for thermal spray corrosion resistant coatings to reduce the likelihood of heat distortion, the use of higher kinetic energy systems, do consider part mass in your product design. This will best ensure dimensional or geometric integrity of your work piece is reasonably held, after coating.