| Organofunctional silanes have retained special attention of the adhesion world for a long time. The current work attempts to expand the areas of application of silanes into corrosion control of metals and alloys.; Studies of selected functional and non-functional silane films formed on iron substrates showed that there is interaction between the amine functional group of gamma-aminopropyl trimethoxysilane (gamma-APS) and the iron substrate, the result of which is no improvement in corrosion protection. A non-functional silane, Bis-triethoxysilyl ethane (BTSE), on the other hand, formed more number of oxane bonds with the substrate, when applied from acidic pH range. This results in improved corrosion protection. A two-step silane treatment consisting of a non-functional first silane layer and a functional silane second layer is proposed, which can provide corrosion protection and adhesion enhancement.; Several alloy systems and bis-silanes are investigated and the two step silane treatment is shown to improve both adhesion and corrosion performance. The selection of the silane application pH is shown to be related to the stability of the metal or oxide surface present. The roles of the first and second layer of the silane are corrosion protection and adhesion improvement with the top-coat respectively.; Concentration of BTSE in the coating solution is shown to affect the properties of the protective film formed on AL 2024. The thickness of the silane film increases proportional to the concentration. Thinner films of BTSE reduce only the cathodic reaction rates at the metal surface, whereas thicker films substantially reduce both anodic and cathodic reaction rates. These results also match several performance tests including ASTM B-117 salt spray.; On Al 1050, the oxide layer on the surface is shown to have little effect on the electrical properties of the BTSE film formed. Preheating the surface and curing of the deposited film strongly influence the electrical properties. The condensation reaction occurring during the curing process results in a hydrophobic silane film. This results in the emergence of a second relaxation in the impedance behavior, which is directly related to the resistance offered by the silane film towards corrosive attack. |
