Phosphate Coating and Phosphating
Phosphate coating is a type of crystalline conversion coating created from a ferrous metal substrate. The coating is used for various purposes and specifically for the purpose of pretreating before painting and coating is done and for increasing the corrosion protection while improving the friction properties of the sliding components. In some instances, the Phosphate coating is being applied against threaded parts and then it is top coated with oil in order to add anti-galling and provide rust inhibiting characteristics.
The process of phosphating mainly relies on the basic pickling reaction which takes place off the metal substrate if the process solution will come in contact with the metals. The biggest benefit that this process can provide is corrosion protection as well as strong adhesion. In general, the Phosphate coating is being used on steel parts as well as on aluminum.
Manganese Phosphate Coating
The metal coating also provides manganese coating, also known as the Type M kind of coating which provides for the anti-galling, lubricity and corrosion protection of metals. Of the various coatings available, it is the Manganese Phosphate coating that is the most difficult in terms of providing unbeatable abrasion and corrosion protection. As compared to Zinc phosphate coating, the manganese phosphate coating provide a continuous wear protection right after the breaking in of components that are being subjected to wearing. Such coatings are being applied by means of immersion. The uses for Manganese Phosphate coating include the production of fasteners, bushings, bearings, as well as other common industrial products. The use of the phosphate is very useful for various projects that will require the sliding of parts, such as the transmission system and automotive engines.
Zinc Phosphate Coating
Another metal coating, is the Zinc Phosphate Coating, also known as Type Z, is also available and is often used for the rust proofing of the ferrous metals. These are also being applied by means of spraying or immersion. In addition, the Zinc Phosphate is a much lighter alternative to the Manganese phosphate and provides resistance against harsh elements that often wear products very quickly.
Types of Phosphate Coatings
The Phosphate coating is available in three different types. There’s the Iron, Manganese and Zinc. Each of these coatings comes with their own unique properties. Both the zinc and manganese phosphates are able to produce more complex layers of crystals, capable of absorbing lubricants more easily. As such, these coatings are more effective in the minimizing of scuffing, pick up and galling. In addition, the iron and zinc are used mainly as under coatings for various metals, especially steel, before they are painted in order to enhance the corrosion protection and paint adhesion.
The Phosphate coating can range from less than 0.1 up to more than 2 mils in thickness. The industry standards often express the coating requirements by weight for every square meter or milligrams for every square foot, instead of the actual thickness of deposit. The coating weight requirement is often dependent on the kind of phosphate process used.