Case Number 101044 - Pulsed Electrodeposition of Silane Films on Metals
Contact: Geoffrey Pinski
Description: This process improves the quality of silane films deposited on metals for the purpose of providing corrosion protection and paint adhesion. Quality refers to uniformity, homogeneity and organization of the molecules.
In silane technology thus far practiced, a metal is dipped into, or sprayed with, a silane solution. The treated metal can be rinsed with water, or can be dried without rinsing. Alternatively, a silane film can be applied by wet rolling, wiping or brushing. Films formed in any of these procedures may be porous and there is not much control over the thickness and the orientation of the silane molecules. Also, the degree of metal cleaning is critical. Patches that are not perfectly clean may not be coated by the silane and thus the performance is degraded.
All of these potential problems can be overcome if the silane is applied by the process of electrodeposition, particularly if the electrodeposition is done in a pulsed mode. Electrodeposition takes place if the metal is positive, in view of the negative silanol groups in a silane solution. The positive pulse will also assist the cleaning process as the metal will dissolve anodically. A negative pulse will lead to a high pH at the surface and the silane will condense (crosslink). This process can be applied to any silane dissolved in water or water/alcohol mixtures.
The advantages of this process are: a more uniform film, the metal alkaline cleaning step becomes less critical and the silane becomes more highly crosslinked.