Stripping

One of the greatest enemies of good welding is contamination. The cleaner you can make your material, the more likely you are to have a successful weld.

Stripping contaminants from metal

For all joins, clean back any coating such as paint or oil to at least 20mm from the join. Regardless of the desired finish, stripping is essential to effective welding. This should be followed by the use of AJAX cleaning powder to remove light oils and dirt.

Mild steel commonly comes either painted or oiled. These coatings are intended to protect the stock from oxidising/rusting in storage and transit. While the steel can be cut, drilled and machined with these coatings still intact, any attempt to weld through these coatings will result in poor weld quality and possible weld failure.

Paint

Often blue in colour, this paint is a barrier to a good weld. The best method for stripping protective paint is the right angle air grinder with surface conditioning pads. Resist the temptation to use an angle grinder or linisher, as this is too aggressive and will most likely deform the surface if not handled carefully.

Oil

Cold Rolled Black and Bright steel often come with a protective oil on its surface. This oil should be ragged off.

RUST

Oxidisation, or rust, needs to be removed. As a rule it is recommended that new stock is used. Where a project requires recycled steel, the material must be assessed for the level of degradation. Only materials with light rusting can be salvaged for welding purposes.

Mill Scale

Mill Scale, a surface by product of hot rolled steel manufacture, needs to be cleaned back with an linisher, angle grinder or surface conditioning pads.

How much do I need to strip back?

It is not necessary to strip the entire surface to achieve successful welds. Only the ends to be joined need be stripped. However, if the project requires further finishing or processes, such as painting, powder-coating, oiling, electroplating, or galvanizing, then it is advisable to clean off all paint on effected areas before welding.

Bear in mind, once steel is stripped of this protective layer it is exposed to oxygen and will begin to slowly form surface rust.