Surface and interface characterization for low temperature plasma interface engineering of aluminum alloy surfaces.

摘要

High strength aluminum alloys owe their improved structural integrity to the addition of alloying elements to an aluminum matrix. In the highest strength alloys, these additions have the unfortunate effect of decreasing the corrosion resistance of the alloy, as compared to pure aluminum. Costs associated with the corrosion of structural materials greatly affect the world's economies, forcing the early replacement or failure of infrastructure components, industrial products, and military weapons systems, to name a few crucial example areas.; Current methods for the protection of structural aluminum alloys employ hexavalent chromium as a corrosion inhibitor and surface passivating agent. This form of chromium is now known to be carcinogenic and it has come under great scrutiny as of late, due to pollution and remediation costs associated with its use. Research toward the development of more environmentally benign corrosion resistant coatings using plasma polymers, as intermediary adhesion and barrier layers on aluminum alloys, is showing great promise as an alternative protection method. These plasma polymer films also exhibit characteristics, in combination with certain conventional polymer coatings, that may lead to the development of long service-life coatings systems.; The integrity of interfaces between each successive coating layer is the most critical factor in the overall performance of any system, given that the coatings themselves are stable. It is therefore necessary to more fully understand the specific chemistry of the surfaces under consideration. Electron spectroscopies allow for the investigation of surface chemistry and, when combined with inert ion sputtering, have the ability to characterize the chemistry throughout an entire film and its interface with a particular substrate. X-ray photoelectron spectroscopy has been employed to investigate the alloy surface modifications from various chemical and plasma pretreatments, the surface and bulk film chemistry of plasma polymers, and the interactions governing their adhesion and corrosion protection enhancement on aluminum alloys. These investigations have given rise to new insights regarding complex interactions with aluminum oxides, elemental enrichment of aluminum alloys, and plasma polymer deposition, modification, aging and adhesion. The culmination of these investigations is presented and addresses the material and surface issues of this research program.