Abstract
When lead compound frit is enamelled on 52S alloy sheet, the sheet must be pre-treated, as reported in previous time, to give it the weather resistance. This is a report concerning study on the pre-treatment methods and the findings are as follows.:
1) Almost similar results are obained through such chemical oxidation methods as alodine method, alrock method, Du Pont method and the method by use of mixed solution of sodium carbonate, water glass and ammonium persulphate.
2) To obtain the whiteness of the enamel, the anodising method is more suitable than the chemical oxidation method.
3) Of anodising methods, the sodium perborate solution method appears to be the most applicable for getting better adhesiveness but the disadvantage of this method is that it needs a comparatively large electric power consumption.
4) In case of using water glass solution, the anodising under A. C. 40V up and 30 seconds at room temperature by use of 4% solution is adequate for good enamelling.
The study on the mechanical properties of enamelled aluminium alloy sheet was also made and the following findings were obtained:
1) In case of 2S-H sheet, being treated at 530°C, while its tensile strength decreases, the elongation increases, as annealed.
2) When 61S-T4 sheet is treated under the same conditions, its tensile strength decreases, but when artificially aged at 185°C for 8 hours, the tensile strength in regained to the point which 61S-T6 sheet has.
3) When 24S-T4 sheet is enamelled 500°C, the decrease in tensile strength is comparatively small.
