Introduction to Chemical Conversion Coatings
Conversion coatings, or chemical conversion coatings, is a common type of metal finishing operation, and a very broad term as well that many common surface finishing techniques fall under. This article aims to offer a comprehensive overview of all that chemical conversion entails, as well as the common types of conversion coatings and their typical uses.
Chemical Conversion: Improving on a Natural Process
Conversion coatings take advantage of a metal surface’s natural tendency to oxidize. They essentially turn the surface of a metal component itself into the protective barrier rather than adding an additional coating layer like other surface finishes. Chemical conversion in particular involves submerging parts in a chemical bath consisting of oxides, phosphates, or chromates. These baths remove a very small amount of the surface metal and replace it with a more homogenous and resilient layer that protects the metal underneath from corrosion.
Typically, conversion coatings are applied through either submersion or spraying, depending on the type of coating and the preference of the applicator.
The Common Types of Conversion Coatings
Anodization
Anodization, most commonly applied to aluminum, is actually a type of conversion coating often applied to improve the aesthetic appearance and corrosion resistance of aluminum components. There are three different types with differing thicknesses and strengths, as well as applications to which they are best suited.
Chromate Conversion or Chem Film
Chem film, also known as chromate conversion, is a type of chemical conversion coating popular in military and aerospace standard aluminum parts. This treatment involves passivating aluminum in order to prepare the surface for further painting or coating, and to protect the parts from conductivity loss, corrosion, and wear. Chem film conversions can also be applied to other metals as well, though aluminum is most common.
Phosphate Conversion Coating
Phosphate conversion is typically applied to steel parts, creating a thin layer of iron, zinc or manganese phosphate that improves the parts’ lubrication and corrosion resistance. Like other types of chemical conversion, it’s also used to improve the adherence of later coatings. Phosphate conversions are common in firearms and similar military equipment.
High Quality Chemical Conversion Coatings from Reid Metal Finishing
Reid Metal Finishing (RMF) is an expert in metal surface treatments, including a variety of conversion coatings such as all types of anodization and chem film (chromate conversion). If you’re in need of chemical conversion coatings for aluminum and other alloys, consider contacting us today!
