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Application guide of passivation process for CNC machined parts
Date: 2022-09-21
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The importance of the passivation process of CNC machining steel parts

Passivation is a method of protecting CNC steel parts from rusting. As a professional manufacturer, Concord is always processing metal parts of many different geometries and sizes according to different materials every day. Such as aluminum, stainless steel, titanium and other metal alloys.

Why can passivation process protect CNC machined steel from rusting?

Why are steel parts more likely to rust before surface treatment? Today, Xiehe will mainly share this knowledge with you through this article. Passivation is essential for steel parts, because it can not only prevent the parts from rusting, but also make the parts look perfect, so the passivation process would be better than other coatings.

What is passivation?

Passivation is a way of surface treatment of metal parts, and its main purpose is to prevent rust and corrosion of steel parts.

Although stainless steel has natural corrosion resistance, it still needs to be passivated to maximize this corrosion resistance. Clean, freshly machined and polished stainless steel parts will automatically form an oxide film by exposure to oxygen in the air. This protective oxide film will cover all surfaces of the part and provide adequate corrosion resistance.

Why is the passivation effect of CNC machining steel better?

Generally speaking, the oxide film does not cover all surfaces of the part, so there are still some contaminants that may be transferred to the surface of the stainless steel part during processing. If not removed, these particles can reduce the effectiveness of the original protective film.

When CNC machining parts, a large amount of free iron will be transferred from the cutting tool to the surface of the part, thus forming a thin layer of rust on the surface of the machined part.

Also, if the CNC machine may contain iron, it will stick to the surface of the part. Maybe this steel part looks shiny, but it still has some invisible particles of free iron that can cause surface rust if exposed to air.

How is passivation done?

Passivation of stainless steel is accomplished by immersing the part in nitric acid, which then dissolves large amounts of free iron or other contaminants on the surface of the part and cleans and re-oxidizes the chromium.

Because nitric acid passivation can produce a better passivated surface, thus maximizing the prevention of rust and corrosion of CNC steel parts. So far, this surface treatment has been widely used in different CNC machining industries.

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