Preparation of material prior to welding
The following conditions apply:
Aluminum and aluminum alloys should not be cleaned with caustic soda or strong
cleaner with a pH above 10. The aluminum or aluminum alloy will react chemically
with these types of cleaners. Other nonferrous metals and alloys should be
investigated prior to using these cleaners to determine their reactivity.
All parts to be repaired and the associated parent metal are to be prepared by
removal of paint at least 50 mm around repair, degreasing thoroughly followed by wire
brushing before fitting and welding.
Wire brushes must be maintained in a grease free condition, and for aluminum must
have stainless steel bristles.
Run on/run off plates must be used wherever possible, unless there is a crater filling
facility on the welding set, or a suitable crater filling technique is used.
Any crater cracking (star cracking) should be removed by dressing. Removal of
excessive material can be replaced by welding as required.
When dressing cracks try to avoid removing too much parent material as the
resulting repair by welding will reduce the number of permissible future repairs.
Welding wire must be kept clean, dry and dust free. When using a set that has stood
for some time unused, sufficient wire must be removed off the spool before welding to
avoid using contaminated wire.
Inter-run wire brushing is mandatory.
Double sided welds must be back chipped or back ground (NOT by any thermal
cutting process) as required, and the root run dye penetrant tested (section 3 c.) to ensure
all defects have been removed. All welding must be allowed to cool before welding the
second side or any subsequent weld runs.
The gas flow rates for welding should be set at:
1.6 mm wire 45-55 cu/ft/hr.
1.2 mm wire 35-45 cu/ft/hr.
These are both relevant for the use of Argon for Aluminum and Argon/CO2 for steel.
Only shaved or chemically cleaned welding wire (Section 4 Table 4-1, Items, 33, 34
and 41 to 49) should be used.
Appendix K Page 4