The depainting dilemma

March 1, 1998

The Depainting Dilemma

Environmental regulations are forcing paint facilities to switch products

By Shanin C. Pepple

March 1998

With environmental regulations on paint strippers looming in the near future, paint facilities across the country are having to search for alternatives. Some facilities have chosen to bite the bullet and make the switch to environmentally-friendly strippers, but others, satisfied with their current selection, are waiting until they are forced to make the change. Regardless of which path facilities have chosen, one fact remains, the aircraft painting and stripping industry will never be the same.

One of the concerns in the aviation industry is the prevalent use of hazardous air pollutants (HAPs) in paint strippers. The Environmental Protection Agency (EPA) created the Aerospace National Emission Standards on Hazardous Air Pollutants (NESHAP), which places restrictions on the use of HAPs in the industry by September of this year. Methylene chloride, one of these HAPs, is used extensively by paint facilities to strip aircraft. Those paint facilities who use methylene chloride, and who have used it for years, praise it for its speed and efficiency.

In addition to the NESHAP, methylene chloride is regulated by the Occupational Safety and Health Administration (OSHA). Under the OSHA Final Rule, employers must ensure that no worker is exposed to methylene chloride in excess of 25 parts per million (ppm) as an eight-hour time weighted average (TWA). The previous exposure level was 500 ppm. The rule also changes the current short-term exposure limit from 2,000 ppm to 125 ppm as a 15-minute TWA. The initial OSHA Final Rule took effect April 10, 1997.

After protest from the industry, OSHA has extended its compliance date for general aviation depainting operations that have more than 20 employees while they evaluate the effects the regulations will have on the general aviation painting industry. This means that employers engaged in general aviation stripping have until Aug. 31, 1998, to comply with the requirement to use respiratory protection whenever an employee's exposure to methylene chloride exceeds the new, lower, eight-hour TWA permissible exposure limit (PEL). OSHA is further extending the requirement to implement engineering controls to achieve the lower eight-hour TWA PEL and short term exposure limit(STEL) until Dec. 10, 1998.

Despite the increased regulations on using methylene chloride, many painting facilities are still reluctant to change — until they have to. While many have switched to products that are composed of less methylene chloride, they don't want to completely switch to environmentally-friendly strippers. However, that doesn't mean they aren't experimenting with these environmentally-friendly, HAP-free strippers.

In fact, larger paint facilities are testing new environmentally-friendly strippers weekly. And that's why some aren't ready to make the switch — they are unimpressed with the alternatives to methylene chloride. They've tried chemical strippers made with water, formic acids, benzyl alcohol, peroxide, etc. They've even tried dry strippers. Those facilities with the time will try almost anything a sales person from a chemical manufacturer offers them. Sometimes the results are promising and sometimes they are discouraging. One thing is for sure: nothing, so far, has been found to directly replace methylene chloride.

Duncan Aviation in Lincoln, NE, is one paint facility that is searching for a replacement for methylene chloride-based strippers. "We're still actively looking for something that will work," says Dan Svoboda, paint production team leader of Duncan. "The other day, we used four different types of strippers on one aircraft. One was 36 percent (HAP), one was 19 percent (HAP), and two were non-HAP strippers."

In the process of its search, the company is sharing its findings with other painting facilities around the country. "Fortunately, because of the size of our company, we can afford to take the time to test new products, but smaller companies don't have the luxury to test new products. We are working closely with three or four shops that are closer to our size around the country and we share the testing of new products."

After testing many environmentally-friendly strippers, many facilities' complaints and concerns are the same: quality, time, expense, and damage to the aircraft.

One of the paint facilities' biggest concerns about using alternatives to methylene chloride is the amount of time needed to strip an aircraft. Since aircraft painting is a business, the companies want to paint and strip as many aircraft as they can in the shortest amount of time. So, the amount of time it takes can affect the amount of aircraft a facility can strip a year. When using methylene chloride strippers, facilities could normally strip an aircraft in one day, but with the alternatives, it takes longer.

Al Gregg, crew leader for Atlantic Aviation in Wilmington, DE, explains: "When we were using methylene chloride, we would come in in the morning and coat the aircraft with the methylene chloride stripper. Within an hour to hour and a half, we would squeegee off the first coat and apply again where needed, power wash, and neutralize the surface of the aircraft all in that single day."

Svoboda agrees. "It takes longer to strip, so we have to change our stripping process. We can't strip in a day anymore; it takes around two days." As a result of this, Svoboda claims that Duncan will paint less aircraft this year. He says the company painted 84 airplanes in 1995, 92 in 1996, and 107 in 1997, but will probably have to settle for about 85 this year. He also says using alternative strippers is an added expense because it takes more manhours to perform the job. He adds that other increased expenses is the cost of some environmentally-friendly strippers and heating the hangar to 90 to 95 F because some of the products are heat sensitive.

However, Gregg says that while it takes more clock time, it doesn't take more man hours to strip an aircraft with an alternative stripper. Atlantic uses a different method. "We didn't have a lot of happy campers to begin with because we looked at it as we were going to lose a day on our schedule. In the beginning, we actually did, but now we've made some other areas after the strip more effective. Because we spent less hours there, we made up that time.

"Now what we do is we coat the aircraft probably an hour before lunch and approximately four hours later we will remove that coat of stripper, reapply it, and leave it on over night . . . We don't put any more man hours on it because while the stripper is working, we assign our men to other areas," he explains.

While most facilities agree on the added clock time when using the environmentally-friendly strippers, there are differing opinions on their performance.

Gregg says Atlantic has already decided to stop using methylene chloride-based products as its primary stripper. "We have gotten away from using methylene chloride strippers all together. We will use it in small quantities where we have areas that we find tough to strip with the nonmethylene chloride-type strippers. We haven't used any appreciable amount in the last year and a half."

He states that the company's current stripper of choice, made up of benzyl alcohol and formic acid, is just as effective as methylene chloride. It strips anywhere from 95 to 100 percent of the aircraft. However, on the spots that don't strip completely, they use methylene chloride. But, Gregg claims, "That is very far and few between. We have a number of jobs that we don't have to use any methylene chloride stripper. It's on a very small percentage of the aircraft hat we have to use any type of methylene chloride stripper at all."

Svoboda says Duncan still uses methylene chloride-based strippers, but they are shooting for a July 1, 1998 compliance to give the company some cushion before the NESHAP takes effect in September of this year. "Where we are now is basically using non-HAP strippers to do large areas and using the methylene chloride strippers to spot strip areas," he says.

Svoboda claims that a lot of environmentally-friendly strippers aren't as effective as methylene chloride, especially on corporate aircraft, because of its paint thickness. He says that the airlines and the military don't have the same problems removing paint with environmentally friendly strippers because the paint is not as thick. "One problem with companies that are promoting new products and the people testing them, is that all the testing is being done on commercial and military aircraft, and these aircraft have very thin paint thickness.

"Environmentally-safe products don't work on the majority of our airplanes. At this time. The problem with aircraft is that on on most corporate jets, the mil thickness of the paint is too great," he states.

As a result of the paint thickness, the paint removal process can damage the aircraft. Svoboda continues, "The problem is that the mil thickness of the paint is not the same throughout the aircraft, so you get a lot of areas that will strip and then some areas that won't strip. And then you have to do a lot of mechanical sanding and you end up removing material from the aircraft." He says that by sanding, the integrity of the skin could be sacrificed.

Besides damaging the aircraft, Svoboda says that some strippers, particularly those that are acid based, can damage the facility and cause harm to workers. He claims that steel grates and concrete floors can begin to deteriorate over time.

Gregg adds that they were originally concerned about the possible effects of environmentally friendly strippers. "We were leery of it to begin with because we were concerned with areas such as the composite and the acrylic windows, etc., but methylene chloride stripper, after it was on for a while, would have the tendency to lift the protective tapes and coverings that were on those areas. Whereas, this doesn't seem to attack the tapes and protective coverings to the point where it lifts and would allow exposure to the chemicals. We were a little hesitant about that because naturally we didn't want to damage the customer's property. But we found that not to be a problem," he says.

While many painting facilities are dreading the day when they are forced to stop using methylene chloride-based strippers, Gregg says that some of the negative reactions are just in anticipation of change. "From my experience here — I've been doing this for 24 years — no one really wanted to make the change even though they knew they had to; it's hard to teach an old dog new tricks. Everybody is hesitant of change of any type and it's really hard trying to make somebody understand that you can leave that chemical on there for that long without damaging the aircraft. (Some of the environmentally friendly strippers) don't have as devastating of an effect on the areas that you are not trying to strip as you would anticipate it to because you are so used to using a methylene chloride-type stripper."

Facilities are still waiting for an environmentally friendly stripper that performs as well as methylene chloride, but most agree that the quality and efficiency of the alternatives is getting better. "I don't think any of the nonmethylene chloride strippers worked real well to begin with," Gregg says. "But like any other technology, it advances and gets better every day."