There are many processes for metals and alloys, which makes precision work difficult without experience and expertise. For example, what is phosphating? Let’s find out what it is and what it is for.
Modern precision turning relies on technical skills, state-of-the-art CNC machines and specific chemical processes to produce quality components. Without certain treatments, it would be impossible to make some metal parts, even everyday ones such as car bodywork.
One of the most important is phosphating, a chemical process designed to protect ferrous metals such as cast irons and alloy steels.
What is phosphating?
Phosphating is a chemical treatment that creates phosphate crystals and deposits them in overlapping layers on a metal surface. What is phosphating for? The aim is to change the surface properties of a metal, improving its resistance to corrosion and wear, reducing friction and making it easier to paint. This is why phosphating is usually used for iron and all ferrous alloys, steel above all.
How phosphating works
Phosphating steel or iron involves coating the metal surface with phosphate-based solutions (e.g. nickel, zinc or manganese phosphates) in immersion or spray systems. Once the surface is coated, a uniform, cohesive protective film of small crystals forms, changing the surface properties.
How thick is a phosphate coating? The protective coating of phosphate crystals is 3 to 10 microns thick, but this is enough to make a significant difference. It creates a protective layer that is less resistant than zinc plating, but provides a perfect base for paint and a durable result.
Types of metal phosphating
The phosphating technique stays the same, but the solution used can lead to zinc phosphating or manganese phosphating.
Zinc phosphating is used to improve paint adhesion and prevent corrosion from weathering, and also improves the appearance of the surface. Manganese phosphating protects parts from seizing between two surfaces and from wear, avoiding sliding problems. One example is machine gears.
How do you know whether the type of phosphating is right for the end use? Surface analysis (salt spray testing) of the metal should be carried out, but in practice it is enough to rely on specialised companies offering a high degree of customisation.