We all use a lot of mild steel in model engineering and so I thought I would list and discuss the surface treatment options:
- galvanizing
- electroplating
- powder coating
- nitriding
- flame spraying
- electrocoating
- painting
Black Surface – there are a number of ways of achieving a black surface on mild steel, one way is to quench the parts in a bath of old engine oil. The other way is to use a chemical gun blue treatment.
Gun Blue – a chemical treatment of the surface that leaves a black finish. This can look slightly rusty and so depending on the use of the resultant part I find it best to lightly oil the surface or use a bees wax after I have a good solid black colour.
Commercially available products such as Perma Blue work rather well, I use a small paint brush to apply it to a well cleaned and degreased surface. Sometimes 2 applications are necessary.
Brown / Copper Surface – heat the part with a blow torch to around 500°C and then quench in a solution of copper sulphate, you will get some areas of copper forming on the surface. Then re-heat the parts to around 500°C and allow to cool. I then just cleaned them with detergent and water before buffing with a small amount of beeswax and a cloth.
References
- finishing.com – a community forum for all sorts of different surface finishes including electroplating.