What is the Importance of Primers in Aircraft Finishing

While it is easy to appreciate the colorful livery found on many commercial aircraft, the most critical layer of paint coating is often overlooked. The primer is an essential first step in painting an airplane, and unlike the topcoat, its purpose is entirely functional rather than aesthetic. In this blog, we will discuss what a primer is and why it should always be used when painting an aircraft.

Aircraft primers, similar to the primers found at any hardware store, are the base coat that creates a foundation and anchor point for all subsequent layers of paint. In addition to its role as a base layer, a primer plays a significant role in the aircraft's aerodynamics, economics, and weight. Furthermore, the primer acts to prevent corrosion and passivate the underlying surface in the presence of moisture. Primers are classified by the various chemicals that make them up and are thus explained:

Red Iron Oxide

This specialty primer was developed to be used on iron and steel surfaces that are exposed to mild environmental conditions. While popular on World War II-era aircraft, its modern use in aviation is very limited.

Wash Primers

Wash primers are readily used on aircraft as they are designed explicitly for the pretreatment of aluminum. Their thin coats have significant passivation capabilities to prevent corrosion and do not require any sanding.

Grey Enamel Undercoat

Compatible with numerous colors and materials of topcoats, gray enamel undercoats are a solid choice for composite areas like the wings, fuselage, tail surfaces, and doors. In addition, this primer dries quickly and does not require any sanding before application.


Featuring the quickest drying times and leading corrosion resistance, urethane primers are becoming a primary choice for aircraft that demand a high level of performance. Moreover, it contains lower VOC levels compared to other aerospace primers and, therefore, is more environmentally friendly. Additionally, certain brands of urethane coatings can also act as a traditional sanding surface in addition to a primer.


With outstanding corrosion and hydraulic fluid resistance, epoxy-based primers are one of the most appealing pretreatment options. Furthermore, it is softer than urethane and thus is less likely to chip and is also highly abrasion-resistant.

Zinc Chromate

This widely recognizable yellow powder was used extensively by the US military during World War II to prime their aircraft. Unfortunately, due to environmental and human health concerns, zinc chromate is less readily available than the other listed options.

When applying any type of primer, it is essential to follow all manufacturer instructions. The first and most crucial step involves the preparation of the underlying material. Neglecting this step will decrease the longevity of the subsequent layers of paint and lessen the anticorrosive effects. Most manufacturers require aluminum surfaces to be scrubbed with an abrasive pad before applying an acid etch solution. These steps provide the primer with an optimal surface to adhere to. Additionally, it is important to note that composite materials such as the wings generally require a more thorough sanding before applying primers.

Choosing the right primer can make a significant difference in the anticorrosive properties and finish of your aircraft. If you are looking to source an aircraft primer from a reliable source, there is no better alternative than Cogent Purchasing. With an inventory of over 2 billion new and obsolete aviation, NSN, and electrical components, we are confident that we can help fulfill your operational requirements with ease. Furthermore, we are owned and operated by ASAP Semiconductor, an AS9120B, ISO 9001:2015, and FAA AC 00-56B certified and accredited enterprise, which means you can rely upon the quality of our products. We invite you to browse our expansive inventory today. If you find a part you are interested in, you can use our Instant RFQ service to initiate the purchasing process immediately.


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