When brazing with silver alloys, the removal of the flux residues can often be rather difficult, due to the incorrect use of the flux: too often the flux is overheated, or insufficient flux is used (the flux on the workpiece will be oversaturated with oxides and becomes very hard), or even the removal itself is done incorrectly.
(Cooling in water makes the flux residues crack and permits an easy brushing away).
Whenever problems occur with flux residues, these residues can be removed easily by using LASTACID.
Brazed workpieces (steel, stainless steel, copper alloys) will be dipped or treated with LASTACID for 5 -10 minutes. LASTACID is used at room temperature, for extreme cases it can be heated up to 50°C (120°F) to obtain quicker results.
For very small or very thin pieces, LASTACID can be diluted with water (two parts LASTACID to one part water).
Workpieces treated with LASTACID must be rinsed thoroughly with cold or preferably warm water.
After drying, the surface will be perfectly clean.
LASTACID contains corrosive elements, so safety precautions are recommended; wear rubber gloves and glasses.
Used LASTACID cannot be dumped into the sewerage.
The acid should be neutralized with lime milk.
Remark: For brazing steel sheets without using flux, Lastek 508 can be used.
