Phosphate coating is a treatment for ferrous substances, eg. castings, iron & steel however not stainless steel. A layer of insoluble crystals is formed on the surface of the metal. Used to provide corrosion protection with or without supplementary treatments; as a substrate for painting or adhesives; to hold lubricants and help break in of parts eg. gears and to prevent galling and seizing.


Zinc Phosphate is the preferred process for conversion coating on steel. It produces fine-grained coating on a wide variety of steel alloys and it increases corrosion resistance. The process can be tailored for particular needs, eg. a light weight coating can be produced which is ideal for surfaces that are going to be painted after coating. However a heavy weight coating can also be produced and is better for anti galling and to carry oils or lubricants for further corrosion resistance. This process is favoured by the oil and gas industry.


Iron Phosphate produces coatings with coarse to fine crystals and creates a receptive surface for bonding. Iron manganese phosphate coating isn’t very good at protecting against corrosion without supplementary protection (normally oil). Whilst Manganese Phosphate is applied chiefly to ferrous parts for break in and to prevent galling. This process is often used for parts that are going to be temporarily stored.

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