Tantalum cleaning surface

Sodium hydroxide (NaOH) and potassium hydroxide (KOH) solutions do not dissolve tantalum, but tend to destroy the metal by formation of successive layers of surface scale. The rate of the destruction increases with concentration and temperature. Damage to tantalum equipment has been experienced unexpectedly when strong alkaline solutions are used during cleaning and maintenance. 

The tantalum layer were prepared by PVD on previously polished substrates. The substrates are degassed under argon atmosphere (450°C, 0.2 Pa for 60 min) and then ionically cleaned (18 min, V = 200 V) prior to the deposition stage at 300°C (0.2 Pa, 4 kW, -50 V polarization). The layer obtained is dense but has a number of defects as nodules and craters dispersed over it s surface. 

As a reference, octadecylphosphoric acid bulk powder pressed onto an indium foil was analyzed with a takeoff angle of 45° with respect to the surface. Both as-received and sputter-cleaned bare tantalum pentoxide substrates were analyzed as reference substrates. 

RE. Bacon and P.M. Moanfeldt, 1963. Reaction with common gases, in Columbium and Tantalum, F.T. Sisco and E. Epremian, Eds., New York Wiley. C.T. Wang and R.T. Webster. 1982. Oxidation-resistant coatings for tantalum. Metals Handbook Surface Cleaning, Finishing, and Coating, Vol. 5, 9th ed.. Metals Park, OH American Society for Metals, pp. 665-666. 

Therefore, all handhng, cleaning, and fabrication practices on tantalum and its alloys should avoid producing such surface contamination, as well as gross contamination. The section on corrosion of tantalum in this book gives more detailed information on the corrosion of tantalum and tantalum alloys. 

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