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Introduction of Stainless-Steel Surface Finishes Technology

2022-04-05 Page view : 11 views

Stainless steel is a multi-purpose iron alloy with excellent wear resistance, corrosion resistance, anti-rust feature and other characteristics and widely used in the chemical industry, mechanical and electrical industry and household appliances industry and more, having a broad prospect. However, the use of stainless steel depends to a large extent on the degree of development of its surface finishes technology.


By finishing the surface of stainless steel, it can provide an extra layer of protection against oxidation, corrosion, rust and staining, while the stainless-steel surface is still smooth and shiny. And the following surface finishes techniques are commonly used.


1.) Black Oxide Scale Removal

During processing, after the plate rolling, binding, welding or heating its surface with high temperature, the stainless steel’s surface will produce black oxide scale. In the past, people used to choose hydrofluoric acid and nitric acid to remove it. But it was eliminated due to its high cost, environmental pollution and human health hazards. At present, the main methods of dealing with this kind of black oxide scale are sand blasting and using chemical reagents. Sandblasting aims to compress air and then get enough power to spray materials speedily – such as quartz sand, iron sand, sea sand, garnet sand, silicon carbon and more – to the surface of the stainless-steel plate, so that its surface can change in nature. The chemical method uses a pollution-free pickling passivation paste and a non-toxic cleaning solution with inorganic additives for dipping and washing as a means of improving the surface finish of the stainless steel.


2.) Mirror Finish

The mirror finish is achieved mainly by mechanical, chemical and electrochemical polishing. Mechanical polishing can remove a very thin layer of metal from the abrasive stainless-steel surface by adding polishing powders to grind and tumble. Chemical polishing can dissolve scratches and abrasions by using chemical reagents, making the surface smooth and flat. Electrochemical polishing is also called electrolytic polishing. It uses the metal workpiece as the anode and electrolyzes it in a suitable electrolyte to selectively remove its rough surface and improve the surface smoothness.


3.) Color Finish

Coloring the stainless steel can not only change its color, but also can improve its wear resistance. The main methods are ion deposition oxide coloring method, high temperature oxidation coloring method and electrochemical oxidation coloring method. Ion deposition oxide coloring method is putting the stainless-steel workpiece in the vacuum coating machine for vacuum evaporation coating. High temperature oxidation colouring method is placing the workpiece in a special molten salt, maintaining a certain process parameter to form a certain thickness of oxide film, eventually showing various different colors. The electrochemical oxidation colouring method aims to form the colour of the film by electrochemical oxidation in a specific solution.