INTERFACIAL ANALYSES OF COPPER CORROSION BY ACRYLIC AND METHACRYLIC ACIDS USING XPS, AUGER AND GRAZING ANGLE FTIR SPECTROSCOPY

We bye observed that methacrylic acid (MA) is far more corrosive than acrylic acid (AA) on copper surfaces when copper was exposed to the va por of these two acids at ambient temperature and environment, With th e aid of modern surface-sensitive instrumentation, which included graz ing angle Fourier transform infrared (FTIR), XPS, x-ray-induced Anger electron and SEM/energy-dispersive spectroscopies and white light ster eo and metallurgical microscopy, we are reporting our results of an ex tensive study of the roles that MA and AA have in this unusual phenome non of copper corrosion. By grazing angle FTIR analysis we demonstrate d that copper carboxylate salt formation is very rapid upon short cont act with the vapor of both acids, and the acids showed no evidence of polymerization. We bye also demonstrated by XPS and x-ray-induced Ange r electron spectroscopy that copper surfaces exposed to the MA vapor c ontains mainly Cu(II)) species. However, the oxidation state of the co pper exposed to AA vapor will depend on exposure time and environment. With limited exposure to the air, the copper surface remained shiny f or up to 12 months test time. The spectrum obtained from the shiny are a of the AA/Cu surface shows that it contains mainly Cu(I) mixed with some copper (II). When the spectrum wets taken from a dull area of AA/ Cu surfaces, the Cu(II) state was found to be predominant. These resul ts strongly indicate that when the shiny AA/Cu surface changed to a du ll color, the oxidation state of the copper also changed from + 1 to 2. The molecular structure of the Cu(II)-AA salt is also believed to be altered. Both stereo microscopic and SEM/energy-dispersive spectros copy techniques were also used to perform the visual and microanalysis of the surface texture and elemental compositions of the corroded sur faces, respectively. The presence of oxygen was also found to play an important role in the overall corrosion processes, The differences in molecular structure of copper carboxylate salts of different oxidation states are discussed and are believed to be responsible for this unus ual phenomenon. We believe that this finding will provide a good expla nation for the cause of drastic differences of copper corrosion by acr ylic and methacrylic acids