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

Ion implantation offers the possibility to alloy the surface-near region 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 consumed too fast. However, for special corrosion conditions a long-term protection may be obtained. Tantalum suffers from hydrogen embrittlement 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 that implantation of electrocatalytically active noble metals such as platinum 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.