TAPPI TIP 0402-32

Abstract

These guidelines cover project and quality-related issues for metal thermal spray coatings installed to prevent aqueous corrosion in pulp mill process vessels, including digesters, flash tanks, evaporators and concentrators. Thermal spray coatings protecting recovery boiler tubes, restoring Yankee dryer surfaces, hard-surfacing calendar rolls, and ceramic ("granite") coatings used on paper machine rolls are not covered by this document, although the basic, application guidelines and qualification procedures described here apply in general to those applications as well. <br>These guidelines describe properties thermal sprayed coatings must have to perform adequately, listing items to include in thermal spray job specifications. Coatings are generically described, mostly according to the spray process. No guidance is given either for choosing the coating process or the coating material for specific service applications. Appendix A describes the most common thermal spray processes.