Thermal spraying: What it was and what it has become

On the eve of celebrating the one hundredth anniversary of its discovery, thermal spraying looks back to its roots - early experiments in which liquids were broken up into fine particles by a stream of high pressure gas. These efforts were directed at producing powders rather than coatings. Schoop first recognized the possibility that a stream of molten particles impinging upon themselves could create a coating. His work, and that of his collaborators, resulted in the establishment of the thermal spray process that has fostered a worldwide industry serving over thirty technology sectors and generating sales of over two billion dollars per year. This article traces the history and development of the principal flame and thermal spray processes.