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Zinc Phosphate Coatings

Sometimes, adding an extra layer before you paint can give your metal surface the added strength you need to get the job done right. While there’s many to choose from, not all are as universally beneficial as zinc phosphate coating.

The Benefits

When you’re preparing metal surfaces for painting or other treatment, Zinc phosphate can provide a sturdy top coat for maximum paint adherence and protection from the elements.

Specifically, this coating prepares the metal surface by providing a solid foundation for additional layers of paint and other treatment to be applied. Not only does the coating serve as an excellent first layer, but it will help ensure your paint stays on longer and even provides a high level of corrosion resistance.

Zinc phosphate coating can be used as a base/primer for:

  • paints
  • other coatings and/or finishings
  • oils
  • waxes
  • Chemical Agent Resistant Coating (CARC)

This coating can also be used in combination with other paints or coatings for additional corrosion protection or to assist in cold-forming processes. While it’s excellent for use with combined coatings and processes, it can also be used as a standalone method of corrosion resistance.


While the specific method of application is determined by your project specifications, Zinc phosphate coating is adaptable to nearly any situation. As a highly versatile material, zinc phosphate can be applied to a metal surface through immersion, spraying, or a variety of other methods. One of the reasons zinc phosphate coating is so popular is its ability to be used across a wide variety of projects, industries, and applications!

Specifications and Uses

Zinc phosphate provides a lighter alternative to other coatings, as well as a variety of benefits well suited to any equipment that might be exposed to extreme environmental conditions.

Despite its lightweight quality, zinc phosphate still provides a high resistance to harsh elements that might otherwise cause products to wear quickly. This combination — its light weight and high resistance to corrosion — make it highly sought after for use across nearly every industry, though it is most highly used among the military, defense, and medical fields. 

The Process

The zinc phosphate coating process is a relatively simple one. The metal being treated reacts with the zinc phosphate solution and creates a durable surface layer made of small crystals. This surface layer provides protection for the material underneath from corrosion, but also provides a strong base coat for any future layers of paint or coatings. This dual benefit is part of what makes zinc phosphate so popular.

The application process also determines the final result of the coating. The zinc phosphate coating process creates a layer of either fine-grain or heavy-grain crystalline phosphates. The grain type of the coating is determined by the application process, which can be adjusted to fit the scope of the project. The variety of application processes available for zinc phosphate coating makes it even more versatile.

Heavy grain: highly absorbent and traditionally used for its ability to prevent rust

Fine grain: traditionally used as a base for paint or other coatings, when necessary

The crystal size (and therefore thickness of the coating) can be influenced by:

  • The cleanliness of the metal
  • The application process used

Therefore, a meticulous and strategic cleaning procedure is used to determine which type of grain is produced by the coating process. The cleanliness of the metal and the specific application process chosen are of the utmost importance in determining the crystal size and thickness of the coating.

Durability and Corrosion Resistance

Zinc phosphate coating is a non-conductor. This means that it prevents current flow and is incredibly resistant to galvanic corrosion. As a chemically produced coating, it is highly resistant to flaking and other types of corrosion over time, making it dependable even as it ages.

Additionally, the colourless coating reflects back ultraviolet rays. This unique feature makes zinc phosphate coating stalwart even in extreme weather or other harsh conditions. 

Adhesion and Base Coating

In addition to weather and corrosion resistance, zinc phosphate coating can adequately prepare a surface for future layers, as it allows for improved paint and coatings adhesion.

The Adhesion Process

The surface of the material must be stripped of any oil or grease and cleaned thoroughly, which creates an ideal bonding surface for treatment free of any contaminants.

This process allows the zinc phosphate coating to be perfectly adhered, creating a solid foundation upon which further paints or coatings can be added. This increases both the quality of adhesion and the durability of the surface.

Considering Your Specifications

For ultimate flexibility, Zinc phosphate has a generic base color which completely frees up your options for future coatings. It is adaptable to nearly any aesthetic and comes in three traditional color variants: dark, medium, and light grey. For additional personalization, coatings to prevent aging or specific colored coatings can be applied.

Some factors might influence how zinc phosphate can benefit your specific project, including:

  • The type and composition of the material you’re using
  • The structure of the metal surface
  • The shape and thickness of the metal surface

These factors can influence the tones and patterns of the zinc phosphate coating and might contribute to a change in tone over time. The real appeal of zinc phosphate coating is its natural look, durability, and adaptability even without additional coatings or treatments.

Choosing Zinc Phosphate Coatings

Overall, the zinc phosphate coating process is ideal for those looking for a high quality surface finish that offers long-lasting durability. 

With zinc phosphate coating, flexibility is key. You’ll find this process suitable for use with a wide range of metals and compatible with a variety of solvents and paints. The fine crystalline coating that zinc phosphate creates serves as an excellent foundation for any subsequent layers of paint or coatings you might need to add to your surface.

 Finally, zinc phosphate coating will be continuously durable even in water, weather, and other harsh conditions. It is for these reasons that zinc phosphate provides such a valuable layer of protection to any surface.

If you’re still trying to determine the exact specifications of your project or want more information about whether zinc phosphate coating is the right finishing for you, we are happy to help! We’ll work with you to meet your goals and determine the best metal finishing for your purpose. We’ll help you get your job done quickly, efficiently, and to your full satisfaction!