Compatibility Chart

Section 4
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Welding Preparation
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Preparation for welding includes storage and handling of aluminum prior to
welding, methods for making the weld preparation and methods for cleaning prior
to welding. While not strictly “welding preparation”, methods for backgouging and
interpass cleaning will be included in this section.
4.1 STORAGE OF ALUMINUM AND ALUMINUM WIRE PRIOR TO WELDING
Improper storage of aluminum and aluminum wire prior to welding makes
preparation for welding much more costly at best. At worst, it can result in welds of
inadequate quality.
It is well known that all aluminum alloys form an oxide coating immediately upon
exposure to air. This coating is extremely thin, approximately 100-150 Angstroms
(one millionth of a centimeter) thick. Because it is so thin, it is not visible to the
naked eye. When stored at ambient temperatures and relative humidity levels of
70% or below, the oxide thickness increases extremely slowly. It is safe to say that
aluminum and aluminum wires stored under these conditions will be usable for a
couple of years. Plus, the reverse polarity arc tends to strip off the oxides. Therefore,
if aluminum is stored in a dry area, oxide removal prior to welding will be very easy
or unnecessary.
However, if aluminum is subjected to temperatures above 200°F (93°C) and/or very
high humidity levels, the thickness of the oxide layer can increase rapidly. Because
of this, the following guidelines are suggested:
» Aluminum wire that has ever become wet should be scrapped. Boxes of wire
where the cardboard box has become wet on the inside should be discarded.
» Aluminum wire should be stored inside, if possible.
» Wire should be stored in the original box and any plastic interior bag it came in.
» It is helpful to store wire in a closed cabinet that is heated to approximately 20°F
(-6°C) above the ambient temperature to reduce relative humidity. This can be
done simply by mounting an electrical fixture with a low wattage bulb inside the
cabinet and letting the bulb burn continuously.
» Wire that will not be used for two (2) days or more should be dismounted from
the wire feeder, returned to its original packaging and stored properly.
Aluminum wire that is stored in accordance with the above recommendations will
be usable, with no deterioration in performance, for at least two (2) years. Wire older
than this should be discarded.
Oxides on an aluminum plate can be removed by power wire brushing, sanding,
grinding or chemical etching; however, please note that proper storage will prevent
the formation of oxides. Aluminum should be stored indoors in a dry environment.