The corrosion resistance of a two-layer polymer (silane+parylene) coating, on implant stainless steel was investigated by microscopic observations and electrochemical measurements. Long term exposure tests in Hanks solution revealed that the coating of 2μm can be successfully used for corrosion protection. However, the addition of H2O2, simulating the inflammatory response of human body environment causes a dramatic destruction of the protective coating. Analysis of the experimental data in terms of circuit models enables proposing a deterioration mechanism. OH ^{radicals formed at the metal surface attack the polymer, thus the deterioration starts from the metal/polymer interface and progress towards the outward surface. © 2010 Elsevier Ltd.}