Thin-film rust preventive

Chemical Properties.6—Tantalum is not affected by air or moisture at ordinary temperatures and does not rust. When the metal is heated in the form of sheet or thick wire in air it becomes yellow at about 400° C.,7 and with increasing temperature blue, and finally black. Above a dull red heat a film of the white pentoxide is produced, which to a large extent prevents further oxidation. Very thin tantalum wire can, however, be ignited in air by a match. In oxygen tantalum wire glows without flame at a white heat, and yields the pentoxide if the pressure of oxygen is greater than 20 mm. The reaction,... 

Soldering is used not only to make a mechanical hond between surfaces but also to provide a leak-proof seal when Uqulds have to he contained. It can also be used to provide a permanent electrical connection. To provide a secure joint, it is essential that the joint surfaces are perfectly clean and free from rust, grease or any other substance likely to prevent good metal-to-metal union. The most likely cause of a bad joint, assuming the surface is clean, is the thin oxide film which is present on all metals. Oxide films can be removed using emery clotb or a flux. 

The bluing of steel has long been used as a process for producing a protective oxide on steel. When oiled and maintained, the thin oxide film prevents the rusting of steel in normal atmospheres. Such oxide coatings can be produced by exposing a clean steel surface to dry... 

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