A new approach to improve high temperature corrosion resistance of thermally sprayed coatings by using electrochemical corrosion tests

Abstract

In order to increase reliability and lifetime of heat exchangers in waste-to-energy plants corrosion resistant thermally sprayed coatings are applied in a higher extent. From the selection of a plant specific spray material and process via laboratory and field experiments up to a successful coating a high amount of time and money is necessary. In particular, experiments in corrosive surroundings at high temperature which are needed to optimize the coating quality are time-consuming. In order to decrease development times and to reduce costs, corrosion resistance of a thermally sprayed coating under high temperature conditions is compared with its behavior in an aqueous solution. If the high temperature corrosion resistance can be forecast by electrochemical tests, a fast, efficient and cheap possibility to improve the coating quality would be available and the efforts for tests in high temperature environments could be decreased. To accomplish this objective, Diamalloy 1005 was sprayed with the APS-process on a ferritic steel. Since the performance of thermally sprayed coatings is not only influenced by the coating material but also by the spraying parameters, three different spray parameter sets were used. After analyzing the results of the corrosion tests under high temperature conditions and in aqueous solution an identical assessment of the spray parameter-specific corrosion protection could be obtained. Ongoing field tests in a waste-to-energy plant are expected to prove the laboratory results. So, a first step in the development of a fast, efficient and cheap method to predict the high temperature corrosion resistance of a thermally sprayed coating might have been done.