Various electrolyte and deposit parameters were investigated to assess the performance of electroless nickel coatings deposited from baths aged in the range 0-6 metal bath turnovers. The properties studied included: measurement of internal stress, analysis of orthophosphite concentration in the plating solution and determaination of phosphorus content in the deposit. The effect of bath ageing on the hardness of the deposit in the as-plated condition, and after heat treatment, was also examined. Changes in the deposit mainly appeared in the range of 3-5 metal turnovers, suggesting that the life expectancy of these lelectroless nickel plating solutions should not exceed 6 metal bath turnovers. The corrosion potential (E_cor) was measured and the corrosion current density (i_cor) of coated samples was determined by extrapolation of polarisation vs.log current density (Tafel) plots in 0.125M H_2SO_4 at 22 deg C.
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