Burnish stainless steel

The burnishing of steel is a common surface refinement. Basically, stainless steel can be burnished, but this is another chemical process. How you can burnish or blacken stainless steel, we have described here for you.

The burnishing of steel and stainless steel

To better understand the difference between the burnishing of stainless steel and conventional steel, we first describe the burnishing of ordinary steel. The following remedies are used to burn metals:

  • acidic solutions
  • alkaline solutions
  • molten salt

The burnishing of stainless steel creates precious rust

In the case of steel, a burnishing rust causes a rust (FeO and Fe2O3). This layer has a thickness of about 1 micron. However, this browning, which is not to be understood as a coating, is very porous and therefore still susceptible to corrosion.

For this reason, bronzed steels are often cared for by greasing or oiling, which results in very efficient corrosion protection. However, if the chromium content in the steel alloy is too high, browning is no longer good, if anything at all.

Blackening and chemically blackening

The blackening or chemical blackening must not be confused with the burnishing. When blackening, the steel is painted with linseed oil and this later burned at temperatures between 400 and 700 degrees Celsius. The metal can also be heated first and quenched with linseed oil. Instead of linseed oil you can also blacken with old engine oil.

The burnishing of stainless steel is actually a black oxidation

The burnishing of stainless steel is similar to the basic principle, but is made with other ingredients, since usually the chromium content of stainless steel alloys is much too high and makes a burnishing in the strict sense impossible. It would also be illogical, because as already mentioned, a steel coating is nothing but a precious rust.

Stainless steel, on the other hand, is stainless steel, so it can be badly "rusted" - at least to a homogeneous rust. For this reason, the burnishing of stainless steel is increasingly called black oxidation. Here nickel atoms oxidize on the surface of the stainless steel.

Properties of a stainless steel black oxidation

This blackening or blackening of stainless steel also has its own specific properties. This oxide layer is smudge-proof on a correspondingly burnished stainless steel and is compatible with alkaline solutions. Unlike acids - even slightly acidic solutions damage this type of blackening considerably.

First test the black oxidation

However, before you blacken the stainless steel, be sure to do a black finish on a specimen of the same stainless steel. The reason is simple: due to the diverse and different alloys of stainless steels, this type of blackening achieves completely different optical properties using nickel atoms. So it is recommended to use a sample to test the optical or color effects of the blackening.

Browning agent from the trade also unsuitable for stainless steel

Now the trade also offers means for burnishing, which can be found especially in arms shops. These are usually means for cold browning. Here, too, the proportion of chromium must not exceed three percent and that the forming layer is a type of rust.

Only the black oxidation or blackening

Thus, these burnishing agents for cold browning can also not be applied to stainless steel. Perhaps then, however, the aforementioned blackening would be an alternative if, due to your stainless steel alloy and the black oxidation does not meet your needs.

Tips & Tricks

Even if steel and stainless steel are closely related, these are completely different alloys with partly contradictory properties. Therefore, we offer many more advice and instructions on how to process stainless steel, especially for stainless steels.

Video Board: How to make a Steel Burnishing Tool