Airplanes are exposed to harsh environmental conditions. At a cruising altitude of 30,000 feet, the air temperature is roughly minus 30 to minus 40 degrees Fahrenheit. The sun’s ultraviolet (UV) radiation is also nearly twice as strong. These conditions, as well as general weather formations, can take a toll on an airplane’s body. Zinc phosphate primer, however, offers a layer of protection.
Overview of Zinc Phosphate Primer
Zinc phosphate primer is a specialized chemical coating that contains zinc phosphate as the primary corrosion-inhibiting pigment. As the name suggests, it’s used as a surface primer.
Zinc phosphate primer isn’t designed to be a final finish. Instead, it’s part of a multilayer protective coating. Zinc phosphate primer is typically applied to bare metal. Once it has fully dried and cured, one or more topcoats is applied over it.
How Zinc Phosphate Primer Protects Against Corrosion
The primary purpose of zinc phosphate primer is to protect against corrosion. Airplanes use many different metal components in their construction. Some of these components are made of aluminum alloy, whereas others are made of steel. When exposed to water and oxygen, metals such as these can corrode.
Zinc phosphate primer protects airplanes from corrosion by forming a physical barrier over metal surfaces. When applied properly, it will completely coat the surface, thereby blocking out water, oxygen and potentially harmful chemicals.
At the same time, the zinc phosphate compounds work via hydrolysis to further prevent corrosion. Zinc phosphate reacts to moisture by dissolving and releasing zinc ions. So, even if moisture penetrates a seal or topcoat and reaches the primer, it shouldn’t cause corrosion.
Paint Preparation
Of course, zinc phosphate primer also helps to prepare metal surfaces for topcoats like paint. It’s designed to etch into metal surfaces. This creates a solid foundation for additional topcoats. When paint is applied directly to metal surfaces without a primer, it may not stick. Some of the paint may drip away, resulting in unprotected areas.
Zinc Phosphate vs Zinc Chromate Primer
In addition to zinc phosphate primer, there’s zinc chromate primer. What’s the difference between them exactly? Zinc chromate primer uses zinc chromate to protect against corrosion, whereas zinc phosphate primer uses zinc phosphate.
In the early years of aviation, zinc chromate was a popular choice of primer. In recent years, however, many aircraft engineers and manufacturers have switched to zinc phosphate due to health and environmental concerns associated with zinc chromate.
