Selectively Strippable: Innovations in the Repainting Process

Repainting an aircraft is a time-consuming and labor-intensive procedure. But PPG Aerospace-PRC-DeSoto plans to change that. It has a selectively strippable coating system that not only provides environmental and application benefits but also reduces...

PPG Aerospace-PRC-DeSoto has introduced a selectively strippable paint system that allows you to remove the topcoat without removing the primer. The selectively strippable system is comprised of three layers: a chromate-free high-solids primer, a chromate-free intermediate coating, and a high-solids polyurethane topcoat.

The primer is formulated to provide corrosion resistance on metal structures. The intermediate coating acts as a barrier and allows the removal of the topcoat for repainting without affecting the primer. The topcoat features increased flexibility and gloss and color retention so the plane looks better longer, according to Alan Schoeder, global segment manager, commercial aerospace coatings, PRC-DeSoto. The topcoat allows airlines to extend the repainting cycle by up to two years compared with conventional topcoats.

“We’ve estimated you can save up to two-and-one-half days on a wide-body using this system just for downtime,” Schoeder says, “not counting chemicals and primers. Savings can range from $100,000 to $150,000 per day. It’s a range based on where it’s located. At the high end at $150,000 a day that’s $375,000. Now, $375,000 for an airline that’s bleeding cash is a big deal. An airline may paint 40 aircraft a year and if half are wide-body, 20 times $375,000 is big money.”

Based on information from customers using the selectively strippable system, there are also savings in materials. The system requires less stripper to take the paint off the aircraft, fewer chemicals for surface preparation, and there is no need to use cleaners, brighteners, sealants, or primers. This can amount to estimated savings of $5,000 to $20,000, according to Schoeder.

Schoeder relates the advantages to maintenance personnel: “the system reduces stripping, it eliminates chromate residue, and the primer and sealant don’t have to be reapplied,” along with the time savings mentioned earlier.

Environmental Concerns

“There’s a tremendous amount of pressure on the airlines and painters,” Schoeder says, “pressure from OSHA and the Environmental Protection Agency (EPA) here in the United States, to reduce chromate exposure and reduced chromate use in the application and removal of paint on an aircraft.”

The removal of chromates has been done in automotive and bridge painting applications which also have tough environments. “But they’ve had a lot of trouble removing the chromate that’s used for corrosion resistance,” Schoeder says. “There’s been some difficulty doing this in aerospace. The problem is that the chromates give some unique protection for the difficult corrosion tests that are run.”

“With an airline such as Singapore Airlines that’s getting the lion’s share of the early A380s, it won’t have to worry about the chromates in the stripper residue, and the benefits include saving primer, not having to worry about applying a chromated primer, and removing the toxic exposure for the painter and the people that are 100 feet away. It’s another big deal.”

When applying a chromated primer you have to be aware of how the area is going to be affected as it’s difficult to control. For example, in Singapore where the weather is hot, humid, and rainy, a hangar door to keep out the cold isn’t necessary. Spraying an aircraft creates a yellow cloud of chromated, pigmented primer overspray that will come rolling out of the hangar and can affect a large area. While painters are protected with personal protection equipment, maybe someone a couple miles away might not be. According to Schoeder, “Most organizations especially in Germany and Japan are saying they don’t want chromates at all. If you have chromates you have to have special ways of containing it to make sure it never gets outside a hangar.”

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