Iron phosphate coating

Depending on the characteristics of the phosphating chemical and the application time; a light yellow, light blue, dark blue or rainbow color is observed on the dried steel surfaces. Iron phosphate coating creates a coating on the metal surface in the range of 0.2–۱ g/m². The processing temperature is not very high.The bath temperature varies between 40 and 65°C depending on the product and application method. A bath pH of between 3.5 and 6 is ideal. A fast, rough coating occurs at lower pH and a softer coating at higher pH.

Iron phosphate provides a high level of protection for the surface under paint, but it does not provide high corrosion resistance on its own. For this reason, the iron phosphate coated part must be dried quickly and painted without delay. Parts that have been waiting for painting for a long time may rust after a certain period of time.

Types of phosphating methods

Phosphating is performed by two methods: immersion and spray for iron, steel and galvanized surfaces. Iron phosphating by immersion is the traditional process that is most preferred due to its low investment cost and simple operation. Iron phosphate coating by spray is the newest and most advanced method. Spray pressure plays an effective role in the surface reaction. Although the initial investment in this process is costly, it offers various benefits, including improved quality, high production speed, and low material consumption.

Iron phosphate coating is one of the preferred phosphating methods, especially in spray lines. Iron phosphate coating is applied before painting and increases the adhesion of the paint to the metal surface. As a result, by coating the metal surface, the paint adheres much better to the surface. Paint that adheres firmly to the surface has high impact resistance. Iron phosphate coating reduces the rate of oxidation that occurs under the paint. Although they offer less corrosion resistance compared to zinc phosphate coating, they are preferred due to the following desirable characteristics.

Features of iron phosphate

1- Less sludge formation

2- Performance at low concentrations

3- Performance at low temperatures

4- Ease of use