The corrosion behavior of pure aluminum in the dilute sodium fluoride and sodium sulfate solutions as simulating the PEMFC environment was studied through immersion process at different time. The corrosion was accelerated in the presence of fluoride ions whereas sulfate ions caused ver y less amount of corrosion. The electrochemical measurement, SEM and EDX analyses were carried out to examine the corrosion resistance, surface morphology and elemental compositions, respectively.

Corrosion resistance and interfacial contact resistance (ICR) of titanium (Ti) bipolar plates for polymer electrolyte menbrane water electrolysis (PEMWE) with dif ferent Au plating thickness were evaluated by potentiostatic polarization in a sulfuric acid solution of pH 3.0. No dissolution of Ti was detected by the ICP-MS analysis (＜1μg dm −3 ) when the Au plating thickness was 0.3μm or more. In the case of Ti with Au plating thickness of 0.1μm, Ti dissolved in the plating defects which were confirmed by ULV-SEM observation. The ICR increased after polarization test for Ti without plating, but not for Au plated Ti even with thickness of 0.1μm. These results indicate that microdefects in the plating layer can be starting points of dissolution of substrate, but do not immediately affect the increase in ICR as far as most of the surface remains covered.

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In order to investigate the effect of pH on the dissolution behavior of iron from stainless steel bipolar plates for PEFC, type 304 stainless steel was polarized in the sulfuric acid solutions of pHs 3.0 and 3.2 for 100 h at 0.6 V (vs. Ag/AgCl) , and the amount of dissolved metallic ions was determined by ICP-MS. In the solution of pH 3.2, more than 90％ of the anodized iron was deposited on the stainless steel surface as corrosion products, whereas about 75％ of the anodized iron was dissolved in the solution of pH 3.0. These results suggest that the contamination of MEA by the dissolved iron is more concerned when the pH of the environment becomes lower than 3.0, while the increase in interfacial contact resistance is rather concerned when the pH is higher than 3.2.