Abstract
In the first part of the continuous studies, the author has reported that the most effective factor in chemical conversion on the surface roughness of aluminium was temperature, and the higher tempetature resulted the larger value of Ra.
In this part, the author followed the changes of surface forms of aluminium with time by chemical conversion in both high and low temperature, and searched for the optimum condition resulting the largest surface roughness of aluminium chemical conversion coatings. For the purpose, the two instruments were used; a microscope and a needle type surface meter for profiling the surfaces and calculation of Ra.
The results obtained were as follows:
1) Microscopic pores which are considered due to pitting corrosion were observed to exist in aluminium chemical conversion coating and their size and depth were different under each treatment condition.
2) Surface form of aluminium in chemical conversion varied with increases in immersion time.
3) The change of surface form was found to be more marked particularly at high temperature.
4) When aluminium was heated at 50°C in deionized water, the value of Ra showed little variation within 30min.
5) When aluminium was heated at 50°C, in 0.01-0.1mol/l solution of triethanolamine, the variation of Ra greatly depended on immersion time.
6) The period of obtaining the largest Ra was about 30-60min. at 50°C, but at 95°C it decreased to 5-15min.
7) The chemical conversion coating formed on aluminium sheet treated in 0.5mol/l solution of triethanolamine at 95°C, for 5min. has the largest value of Ra.
