Aircraft painting extends beyond aesthetics; paint protects the airframe’s integrity and affects the aircraft’s weight. The topcoat finish protects the aircraft’s exposed surfaces from deterioration and corrosion. Additionally, an aircraft that’s properly painted is easier to maintain and clean as the exposed surfaces have higher resistance to dirt and corrosion, and oil doesn’t stick to the surface as readily.
A broad range of materials is used for aircraft painting and finishing that provide the airplane with the desired appearance and protect its exterior. The term “paint”, used in general sense, includes lacquers, enamels, primers, and different multipart finishing formulas. There are three components in paint – resin as the coating material, solvents for reducing the mix to reach a workable viscosity, and pigment for color.
Unexposed components and internal structure of an airplane are finished to safeguard them from deterioration and corrosion. All exposed components and surfaces are finished for an aesthetic appearance and protection.
Classification of Aircraft Paints
This post is focused on the classification of aircraft paints. Following are the chief types of paints used for aircraft painting:
When fabric-covered airplanes were predominant, the standard finish used for protecting and coloring the fabric was dope. Dope provided several qualities to fabric covers, such as increased tautness, UV protection, weather-proofing, airtightness, and tensile strength. Essentially, aircraft dope is a colloidal solution consisting of cellulose nitrate or acetate mixed with plasticizers to form a homogenous, flexible, and smooth film.
Dope is still employed on fabric-covered airplanes as part of the covering process. Nevertheless, the fabric type being used for covering the airplanes has changed. Linen or grade A cotton was used for years as the standard covering. It may be used still if it fulfills the FAA (Federal Aviation Administration) and TSO (Technical Standard Order) C-15d/AMS 3806c requirements. The aviation industry is now dominated by polyester fabric coverings. Especially developed for aircraft, these new fabrics are far better than linen and cotton.
2. Synthetic Enamel
Synthetic enamel – a single-stage, oil-based paint for aircraft exterior painting – offers protection and durability. The shine and durability can be increased by mixing it with a hardener while lowering the drying time. Synthetic enamel is an economical type of aircraft finish.
Lacquer’s origin dates back to hundreds of years. Lacquer originated from a resin which is obtained from certain trees that are indigenous to China. Nitrocellulose lacquer was made in early 1920s through a process using wood pulp and cotton.
Nitrocellulose lacquers result in a semi-flexible, hard finish which can be polished for obtaining a high sheen. With aging, the clear variety may yellow, and it can also shrink over time leading to surface crazing. In the automotive industry, lacquer was the first type of coating used in mass production, since it diminished the finishing times to two days from about two weeks.
To resolve the yellowing problems, acrylic lacquers were made. The working properties of acrylics are almost the same, but on drying, the film is more flexible and less brittle than in case of nitrocellulose lacquer.
Lacquer is an easy paint to spray as it’s quick to dry and its application can be performed in thin coats. Lacquer, however, is not a highly durable paint for airplane painting. Gasoline spills, acid rain, and bird droppings can eat down into it.
Lacquer’s current use for aircraft exterior coating is almost nonexistent due to environmental and durability concerns. About 85 percent or more of the VOCs (Volatile Organic Compounds) in spray gun are released to the atmosphere when lacquer is used, and its use has been banned by some states.
Some lacquers have been developed recently that employ a catalyst, but these lacquers are mostly used in the furniture and woodworking industry. These are nitrocellulose lacquers with ease of application due to much better abrasion, chemical, and water resistance. Moreover, lacquers with catalyst cure chemically, not through evaporation of solvents only. So, the VOCs emitted into the atmosphere are reduced.
Polyurethane is the best option when compared to aerospace paint of other types, for its properties of chemical, stain, and abrasion resistance. The wet look was introduced by polyurethane. It exhibits a high natural resistance to UV rays’ damaging effects. Usually, polyurethane is the preferred option for corporate aircraft painting and finishing in the aviation environment of today.
5. Urethane Coating
The term urethane refers to certain binder types used for clear coatings and paints. Urethane is typically a coating in two parts consisting of a catalyst and base, which when mixed, generate a high-gloss, durable finish with chemical and abrasion resistance.
6. Acrylic Urethanes
Acrylic means plastic. It provides a harder surface on drying but its resistance to harsh chemicals is less than that of polyurethane. Most of the acrylic urethanes require the addition of extra UV inhibitors when subjected to the sun’s UV rays.
These are the key types of aircraft paints. If you need your airplane painted, consider choosing one of the most reliable aircraft paint shops so that your airplane gets the finest quality painting.