Swarf is the debris created when you cut, drill or smooth metal, somewhat like sawdust but requiring more diligent cleanup. It can cause injury, stick to metal surfaces, get into machinery, or otherwise cause all sorts of headaches if it isn’t dealt with properly.
The heat generated in the cutting process can make swarf stick to metal surfaces. Some cutting processes include liquids designed to reduce the impact of swarf while other processes remain dry and leave swarf on shop surfaces and parts.
Impact on Coatings
Swarf generally doesn’t cause problems with finishes on pre-painted steel. The stain from the swarf tends to be absorbed although the look of the metal may then not be as smooth.
However, on metallic coatings containing zinc, the surface can become pitted and rusted because the zinc becomes tied up with the swarf, leaving the surface unprotected. In damp or humid climates rust spots will soon appear.
Repairing Swarf Damage
Minor Staining on Pre-painted Metal: A household cream cleaner will generally remove these stains. Follow the directions on the cleanser container.
Heavier Staining on Pre-painted Metal: This takes a little more work.
- Surface clean with a non-ionic industrial or household detergent and water.
- Rinse well.
- Remove corrosion with a stiff nylon brush; do not damage the paint.
- If needed, lightly rub with a rough pad such as Scotchguard™. DO NOT USE STEEL WOOL.
- Rub with phosphoric-acid based solution.
- Thoroughly rinse with clean water, preferably with a hose.
Mild stains may still remain.
Extensive Staining on Pre-painted Metal: The easiest solution may be to paint over the stains. Before painting, remove any remaining swarf from the surface or rust will bleed through the new paint. Repaint the entire area for visual consistency. This surface may weather differently from the pre-painted.
Metal Coated Steel:
- Brush carefully with a non-metallic, stiff bristled brush to get rid of remaining swarf. DO NOT USE STEEL WOOL.
- During the installation of a metal roof it is highly recommended that the roof be swept clean as it is being installed. This will prevent any staining overnight when the dew will cause the swarf to rust very rapidly.
- Paint immediately to cover marring.
Swarf contained in lubricated processes can be difficult to deal with. Cutting fluids and coolants with swarf can be sludgy and hard to clean. Chip wringers and centrifuges can be used to separate and compact the metal filings which can then be dried down and more easily disposed of.
Swarf created in a dry environment can be a little easier to deal with. Magnetic products such as wands make clean-up easier and safer for the worker. The collected swarf can then be ground further by a chip breaker, shredder, or crusher and compressed into a block for disposal or recycling.