OPTIMIZATION OF THE NICKEL FLUORIDE COLD SEALING PROCESS

This paper investigates the effect of varying sealing parameters, in order to optimize the conditions used to achieve a good seal quality for nickel fluoride cold sealed anodized aluminium. The effect of time, temperature and solution pH on seal quality was studied by British/ISO standards tests such as phosphoric acid/chromic acid, dye absorption and admittance. The quantity of nickel absorbed in the pores of anodic films as a function of solution parameters was measured by Atomic Absorption Spectroscopy (AAS), in order to find out the relationship between seal quality tests and nickel absorption. Although all the sealing parameters were found to have an effect on sealing quality and quantity of nickel absorbed in Me pores, the major eff-t resulted from temperature which was found to be critical. The best results were found to be at a temperature of less-than-or-equal-to 25-degrees-C for a 20-mu-m film. The quantity of nickel absorbed in the pores as shown by AAS, tends to correlate with the results of the seal quality tests. The effect of post-treatment (final rinse) with hot deionized water (70-degrees-C) was also investigated. The Post-treatment was found to accelerate the aging of cold sealed finishes and the results of optimized cold sealed samples which have been post-treated are very promising for commercial use.