Metal burnishing: what it is and how it happens

Minifaber uses the best suppliers for metal burnishing. Let's see what this is all about and how this process is carried out on a practical level.

There are several metal surface treatments such as galvanizing, silvering, phosphating and so on. In this article we will focus on burnishing, a treatment that improves the aesthetic appearance of processed metals and protects them from corrosion:

• What is the metal burnishing process?
• How it is carried out;
• The manufacturing of finished and semi-finished products in Minifaber;

Minifaber does not perform the metal burnishing process internally, but relies on suppliers who have in-depth expertise in the field of metal surface treatments. 

What metal burnishing is?

Burnishing is a chemical surface treatment for blackening metal parts such as iron, brass, aluminum and carbon steel. It improves the aesthetics of the part and makes it immune to corrosion from weathering and substances. Once darkened, the metal acquires a glossy blue-black color. The treatment does not involve any thickness carryover and can be barrel or static depending on part compliance and/or customer requirements.

Burnishing process on ferrous materials

Except for stainless steel, burnishing treatment on ferrous materials is carried out by immersing the piece of iron or steel in water enriched with lead acetate, sodium hyposulfite and other substances which may vary in quantity according to the metal to be treated and the color it should take.

The burnishing of iron and steel can also be obtained by immersing the hot piece in oil and, once burnished, heating it slightly and then letting it cool down to room temperature.

Burnishing process on non-ferrous metals

On non-ferrous materials such as copper, brass and bronze, the burnishing treatment can be carried out using a solution of potassium sulfide, simply by immersing the pieces, clean and degreased, even cold for a few minutes and then rinsing them in running water.

How burnishing is carried out

In the past, the burnishing process was carried out in a coarse manner, exposing the piece to be burnished directly over a flame, removing it when the desired blue color was reached. Today it is carried out through galvanic treatments and immersion in chemical baths, much more sophisticated and precise processes that give the piece the necessary resistance to atmospheric agents.

Metal burnishing can be performed either hot or cold. With the support of its experienced suppliers, Minifaber can perform both burnishing treatments. 

• In hot-burnishing, the maximum process temperature is 113 °F: the pieces are normally delivered oiled. If necessary, the oil can be removed and replaced with other products, waxes, varnishes or oils of a different type. 

• Cold burnishing, on the other hand, takes place without heating the metal, at room temperature: it is obtained by converting the metal layer into a black oxidation with a depth of 1.3 to 3 microns. 

Manufacturing of finished and semi-finished products in Minifaber

Minifaber is one of the few companies able to design and manufacture finished, complex, assembled products following metalworking and surface treatments such as metal burnishing. It is not common nowadays to find a partner able to deal with metalworking from the moment of the customer's custom request to the delivery of the finished product ready for the market. 

Minifaber manufactures, for example, coffee machines, flame diffusers for boilers, sterilizers, weft wire accumulators for textile looms and much more.