抄録
Studies on aluminum enamelling carried out heretofore have so far revealed that the most important factor is the pretreatment of the aluminum plate. As reported in the first paper, the anodic film coated by means of anodic oxidation in dilute sodium perborate solution had satisfactry properties, both in adhensiveness and luster.
In the present studies, further investigations have been carried out as follows:
α-alumina coating has been made by submitting the aluminum plates to anode treatment in the aqueous solution of borate (sodium perborate, lithium borate, Na-borate, K-borate, etc.) or silicate (water glass) of B2O3, SiO2 (glass net-work formers), Na2O, Li2O, K2O, etc. or Li Na, K, etc. (glass modifiers). Mixed aqueous solutions of these borates or silicates have also been used. When the aluminum enamel flit is applied on these surfaces, it was expected that a semi-glass net-work former would be produced between the α-alumina and the flit, and that an improvement in adhension would be obtained.
The results may be summarised as follows:
(1) Impact test
Lithum borate, sodium borate, water glass, and potassium borate were the most effective in mono-component aqueous solutions. Amongst binary mixtures, the system lithium borate-water glass was the most effective. Furthermore, ternary mixture also gave satisfactory results.
(2) Bending test
Sodium borate, lithum borate, potassium borate, and water glass were the most satisfactory compounds in aluminum enamelling in mono-compound aqueous solutions. Among binary mixtures the above mentioned system was the most effective.
Among ternary mixtures, aqueous solutions containing sodium borate-water glass as the main constituent gave especially good results.
(3) Thermal shock tests
Similarly to the cases (1) and (2), treatments with mixtures were superior to those with mono-component solutions.
Aqueous solutions containing potassium ions were satisfactory in all cases.
Thus samples submitted to anodic treatment in mixed solutions showed superior results in every respect to those treated in mono-component solution.
