Tantalum Protective Thin Coating Techniques for the Chemical Process Industry: Molten Salts Electrocoating as a New Alternative

摘要

A comparison of corrosion resistance and basic properties of solid tantalum with other high-performance materials used in the Chemical Process Industry (CPI) is given. The corrosive chemicals taken into consideration are strong acidic media. Secondly, it is pointed out that tantalum, which exhibits excellent corrosion resistance, owing to a rapid build-up of passivating protective film in oxidizing conditions, also has good mechanical, thermal and electrical properties which suggest its use when little or no metallic corrosion is tolerated. Thirdly, tantalum thin-layer, coated onto a usual base metal, which offers the same protection as solid metal and avoids its expensive use, is treated. Fourthly, numerous tantalum-coating techniques for clad-vessel and CPI devices are reviewed and compared. Amongst these coating techniques, this paper focuses mainly on two techniques which give a very thin, protective coating against corrosion. Thus, Chemical Vapor Deposition (CVD) and Molten Salt Electrodeposition (MSE) are especially enhanced. Finally, MSE which is still not widely used for manufacturing clad-vessels is examined in greater detail.