Iron Phosphating VS Zinc Phosphating

Published by admin | Filed under Engineering

According to precision engineering technique, the phosphating process forms a layer of insoluble phosphates on a metal surface using an agent containing phosphoric acid and/or phosphates. Zinc phosphate can offer a performance enhancement over iron phosphate however; this will come at the cost of higher capital expenditure and higher operational maintenance.

Iron phosphating, used to provide steel surfaces with good adhesion to paints.
Zinc phosphating, used against corrosion and as pre-treatment for steel and aluminium surfaces, prior to painting or oiling for cold flow pressing and Mangano-phosphating which delay the adhesive wear of mechanical parts of internal combustion engines, or bearings.

In precision engineering services additional stages are involved into phosphating process, due to this the zinc phosphate process will require more maintenance of equipment and waste. With additional stages, there will be more tank dumps, waste and waste disposal to consider. Also, the zinc phosphate stage will generate a considerable amount of sludge that will need to be removed and disposed off. Chemical maintenance of the zinc phosphate stage is also more difficult since it requires you to monitor the extent of oxidizer present, and then add back separately from the zinc phosphate.

Phosphate coatings may be applied to metal substrates, particularly ferrous substrates, by reaction of the substrate with an aqueous acidic solution of certain metal phosphates, e.g. phosphates of iron, manganese and zinc. There are certain by-products of the reaction with the substrate some of which are precipitated from the phosphating solution as coating proceeds. Precision engineering company uses these by-products which include an insoluble phosphate salt of the substrate metal, for example ferric phosphate in the case of a ferrous substrate.

Phosphate coating produces a chemical conversion on the surface of carbon steels and capable of performing some significant features among other precision engineering services like:

• Reduces galling and risk of attack
• Improves lubricity and oil retention of applied lubricant films
• Provides an excellent key for subsequent paint or sprayed on coatings
• Increases corrosion resistance