Plasma transferred wire arc (PTWA) thermal spraying is a thermal spraying process that deposits a coating on the internal surface of a cylindrical surface, or external surface of any geometry. It is predominantly known for its use in coating the cylinder bores of an internal combustion engine, enabling the construction of aluminium engine blocks without cast iron cylinder sleeves.
The inventors of PTWA received the 2009 IPO National Inventor of the Year award. This technology was initially patented and developed by Flame-Spray Industries, and subsequently improved upon by Flame-Spray and Ford.