A-Coating: an Organic Process providing a strong, protective finish

protective metal finishes series

Manufacturing industries, especially metal fabrication and assembly, are naturally prone to corrosion. Metal surfaces exposed to moisture or other elements experience a chemical reaction and corrode. Dirt, oil, grease, and other contaminants speed this process up on metal surfaces. 

The protective effect of galvanic zinc coating is negligible when raw steel and zinc are in contact with each other because of galvanic action and hydrogen embrittlement, making it necessary to provide an intermediate protective coating between bare metal surfaces and zinc coatings. 

Now Autodeposition, more commonly known as A-Coating, enters our story.

A-Coating Process

A-coating differs from traditional e-coating because it does not require metal pre-treatment with electricity to form the coating. Instead, an organic layer forms from degreasing the metal surface with a mixture of water, water vapor, and natural and non-organic substances. Figure 1 summarizes a typical a-coating process.

a coating process and sequence

The dipping process evenly coats complex components from the inside out, covering a complete assembly of different materials. A mixture of two iron ion chromosomes in a set of four is coated with acid using an electrically driven coating process.

An Autophoretic® coating applies to a metal surface using a water-based method to deposit an organic polymer emulsion chemically. The organic material is not in direct contact with the metal material, forming a chemical compound, creating an organic polymer emulsion when ions from the latex interact with the steel part’s surface, coating it.

Because the surface is very porous, chemical activators reach the steel surface and disperse, forming superior corrosion resistance and surface protection through repeated coating. 

Controlling Application Thickness

Control over the amount of material deposited on the metal is important for specialized industries because maintaining consistent thicknesses reduces material waste.

There are four ways to control the thickness of the substrate:

Immersion Time

When steel is immersed for an extended time, the coating process slows down and stops because of the diffusion of ferrous ions from the surface and ferric ions to the surface. The protective coating is based on the diffusion of ferrous and ferric ions.


A mechanical mixer stirs the ions at the chemical bath surface, which contributes to a significant number of ions being deposited by adjusting the mixer speed.

Using Activators

Adding activators increases the reactivity of the chemical bath.

Industries Using A-Coating

Many industries use A-coating, including:

  • Defense and machine supporting industries
  • Automotive and ancillaries
  • General engineering
  • Heavy earth moving equipment manufacturing
  • LCV/MCV/HCV auto service
  • Heavy earth moving equipment
  • Power Equipment
  • Aviation and marine components

A-Coating Advantages

The A-coating process offers several advantages. These are:

  • No Limits: An electric charge is moved on a conductor’s surface by an electromagnetic field generated by the coupling of electric and magnetic fields. An electromagnetic field influences a current on the conductor’s surface, resulting in electrical shielding. Electrical shielding doesn’t limit the a-coating process—anything the coating touches becomes coated.
  • Easily Coating Complex Products: The immersion process ensures complex products are completely coated.
  • Hard Barrier: Wear resistance is exceptional because of its rigidity and direct connection to the substrate.
  • Environmentally Friendly: A-coating is VOC-free and has minimal environmental impact.
  • Curing Temperature: Full coverage occurs when coating composite parts and assemblies at a temperature of 220 ºF.
  • No Power Required: No electricity is required to complete the process. Instead of relying on the current, a chemical reaction takes care of the job.

In Sum

Autodeposition is a very effective method for applying protective coatings. Its materials are also flexible, making it suitable for various applications.

However, not all coating applications are equal, and you’ll need to choose the most appropriate coating system to achieve the best results.

For example, if you need a corrosion protection coating on a large surface area, Autodeposition is a great option. But other deposition methods may be better if you need a protective coating on a smaller, more intricate surface.

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