If
material is known to have been exposed to sulfur
compounds or low-melting-point metals,
chemical cleaning methods may be required to
remove the contamination, because grinding
may smear contaminants into the surface. Thermal
cutting methods, such as plasma arc, laser
beam, or air carbon arc, may be used to prepare
bevels, but the cut surfaces should be ground to
bright metal prior to welding. Oxyfuel cutting is
not effective on nickel alloys