ELECTROCHEMICAL AND CORROSION PROTECTION PROPERTIES OF ION-IMPLANTED THIN-FILMS

Ion implantation offers the possibility to alloy the surface-near regi on of metals with noble metals which increase the corrosion resistance of the system. Due to the limited entrance depth of ions into solids, the modified zone is generally very thin. The observable effects are therefore usually not long-lasting because the resistant alloy is cons umed too fast. However, for special corrosion conditions a long-term p rotection may be obtained. Tantalum suffers from hydrogen embrittlemen t when it corrodes in hot concentrated mineral acids, and titanium and stainless steel from active corrosion with high dissolution rates in activating mineral acids. Electrochemical and immersion tests show tha t implantation of electrocatalytically active noble metals such as pla tinum and palladium may lead to an effective protection over a longer duration of time. For comparison, results on uniform corrosion of iron in slightly acidic media are also discussed.