Development of thermal spraying materials through several corrosion tests for heat exchanger tube of incinerators

• New thermal spraying materials for heat exchanger tube were developed.
• The corrosion resistance was evaluated through several corrosion tests.
• Coating of Fusible Ni-SA-c exhibited excellent corrosion resistance.
• The measurement of contact angle can predict the corrosion resistance.

Protective surface treatment via several kinds of cost-effective thermal spraying alternate materials was developed and investigated in this study for heat exchanger tubes in waste incinerators with quite aggressive environment. Different thermal spraying materials including Fusible Ni-SA-a, Fusible Ni-SA-b, Fusible Ni-SA-c, NiCr-TS and NiCr-WEL were investigated to evaluate their performance of corrosion resistance. Three corrosion tests including high-temperature wettability test, long-term adhesion force experiment and hot corrosion test were performed, respectively. As has been proven from experimental results, the specimen coated with Fusible Ni-SA-c exhibited high contact angles in both air and simulated flue gas condition, which indicated a low ash wettability and liquid-bridge force. The coatings of Fusible Ni-SA-c and Fusible Ni-SA-b resulted in quite low adhesion force between ash and specimen, illustrating their good performance to improve the tube corrosion resistance. Besides, the weight losses of specimens coated with Fusible Ni-SA-c and Fusible Ni-SA-b due to corrosion by ash were noticeably decreased, in particular Fusible Ni-SA-c caused almost zero corrosion. Fusible Ni-SA-c decreased the amount of ash deposition on the tube surface of SUS304 by 35%. These corrosion tests supported Fusible Ni-SA-c as thermal spraying material with excellent corrosion resistance, which is able to prevent the heat transfer surface from high-temperature corrosion and thus enhance the service-life of the tube. Furthermore, among these corrosion tests, it was found that the high-temperature wettability test is an effective approach to evaluate the performance of different corrosion-resistant materials.