| 摘要 |
Iron or mild steel is treated to improve the adhesion of vitreous enamel by depositing a coating of nickel thereon, subjecting it to a scale anneal, at least equivalent to that obtained by heating in an atmosphere of burned natural gas containing 11 per cent combustibles and a dew-point of 150 DEG F, at 1550 DEG F for 2 minutes, and then removing the scale by pickling. The nickel coating may be formed by deposition from a 30-40 per cent solution of nickel sulphate or by electrodeposition. The scale anneal may be a normalizing treatment in air, or may consist in holding at 1700-1800 DEG F for 40 seconds and cooling to 900 DEG F in 2 minutes in an atmosphere containing 9 per cent carbon dioxide, 5 per cent carbon monoxide, 12 per cent hydrogen and the balance nitrogen. The pickling solution may be a 6-25 per cent solution of sulphuric acid at 160-190 DEG F. The metal may be decarburized at any stage in the process and may be given a final flash coating of nickel by chemical deposition before coating with a single layer of white or light-coloured vitreous enamel. |
