K. Murakami, M. Shimada, National Maritime Research Institute, Mitaka, Japan
For the purpose of development of thermal spray coatings with corrosion protection and antifouling properties, aluminum-copper alloy powders, aluminum-copper blend powders, aluminum-zinc blend powders and a zinc powder are flame sprayed onto a steel substrate and the coatings are immersed in the sea. Some of the substrates are treated with an aluminum under-coat prior to the spraying of the above-mentioned coatings. In the sea, barnacles adhered to the aluminum-copper alloy coatings of copper content lower than 20 mass% and to the aluminum-copper blend coatings of the copper content lower than 40 mass%. Rusting of the steel substrates occurred in the case of the coatings of higher copper content. The zinc coatings and the aluminum-zinc blend coatings with zinc contents over 50 mass% possess both corrosion protection and antifouling properties. It was found that the application of the aluminum under-coat promotes the corrosion of the top-coats.
Summary: For the purpose of development of thermal spray coatings with corrosion protection and antifouling properties, aluminum-copper alloy powders, aluminum-copper blend powders, aluminum-zinc blend powders and a zinc powder are flame sprayed onto a steel substrate and the coatings are immersed in the sea. Some of the substrates are treated with an aluminum under-coat prior to the spraying of the above-mentioned coatings. After the immersion of the coatings in the sea for five months, barnacles adhered to the aluminum-copper alloy coatings of copper content lower than 20 mass% and to the aluminum-copper blend coatings of the copper content lower than 40 mass%. Rusting of the steel substrates occurred in the case of the coatings of higher copper content. The zinc coatings and the aluminum-zinc blend coatings with zinc contents over 50 mass% possess both corrosion protection and antifouling characteristics. It was found that the application of the aluminum under-coat promotes the corrosion of the top-coats.
