Plasma cutting
Attention must be paid to a most focussed arc and a lowest possible heat input. Especially with alloys of the 2XXX, 6XXX and 7XXX groups cracking may occur in the heat affected zone and machining of the cutting edge of up to 3 mm and more may be required. Alloys of the groups 1XXX, 3XXX and 5XXX can usually be welded without any post treatment.
Machining
Turning, milling or other metal-cutting processes are most suitable. Lubricants or cooling liquids must not be used, however, and the tools need to have sharp edges to prevent smearing of the metal. For sawing and grinding products shall be used only which are recommended by their manufacturers therefore. With brushing care needs to be taken that stainless steel brushes are used to prevent inclusions of Carbon steel into the base material. The wire diameter of the brush should be between 0,1 and 0,25 mm with the softer Aluminium alloys and between 0,25 and 0,4 mm with the harder alloys. If the wire is too thin then it is often bent at its ends and therefore is not longer able to remove the impurities. It gives rather a smearing effect. If the wire is too thick then it leads to flutes in the material. Similar considerations are to be taken with shot blasting. Compressed air tools should exhaust to the back in order to prevent a contamination with oil.
Chemical cleaning
The cleaning processes should be applied short before welding. Possible methods of cleaning are pickling in alkaline solutions and the application of solvents on a Carbon-Hydrogen basis (Alcohol, Acetone etc.). In spite of the high effort pickling is to be preferred. The use of solvents is questionable in respect to work safety. Residuals of solvents can be converted into harmful gases and fumes during arc welding.