GB624369A - Improvements in and relating to soldering metals and alloys, more particularly thosethat are difficult to solder - Google Patents

Abstract

In coating metals or alloys particularly those difficult to coat such as aluminium or its alloys, chromium or its alloys, zirconium, or magnesium alloys, the metals &c. are coated first with a solderable metal layer by burning on with a glaze, and then with molten metal such as by dipping in molten zinc. The solderable layer may be effected without first removing the oxide on the article, and anodized aluminium articles may then be coated. A suspension of enamel and metal such as silver, copper, platinum, gold, or compounds thereof may be painted or sprayed on to the object and then burnt on in a manner similar to coating ceramic materials. As an alternative a layer of enamel may be first applied and then a metallizing suspension. Where the surface is still difficult to solder after burning on a glaze containing metals, a further metal layer free from glaze may be burnt on. In a further form a glaze containing a metal suspension may be first applied and dried, a coating of glaze-free metal suspension then applied, and burning on then effected to fix the coating. An aluminium plate may be sprayed with a suspension formed of 200 grams of borosilicate enamel containing 5.6 per cent of SiO2 14.8 per cent of B2O3, 71.4 per cent of PbO, 1 per cent of H2O3, 1.4 per cent of ZnO, and 2000 grams of silver or silver oxide in 1000 grams of ethylene glycol to which 50 grams of nitrocellulose is added. After drying, a layer of silver or silver oxide free of enamel is sprayed on and after drying the second layer, heating is effected for 10 minutes at 500 DEG C. The surface prior to coating may be pickled or sand blasted. Sleeves or tubes of aluminium may then be used in the manufacture of coils, transformers potentiometers and other electrical parts and for kitchen or household articles.