Crop duster corrosion

Crop Duster Corrosion Written by Jeremy R.C. Cox, A&P IA and ex-duster pilot. November 1998 In order to understand corrosion on crop dusters, it is helpful to understand a bit about the chemicals that the aircraft is being exposed to...

When I spent a year teaching at a crop dusting school in Oklahoma, we instilled into the minds of all student duster pilots, the importance of keeping their aircraft fastidiously clean. After every flight, each student would wash their Ag aircraft. At this time, they would be inspecting for any corrosion that might be starting to infect their machine. In addition to religiously washing their aircraft they would polish the inside of their engine cowlings as well. This additional action made it easier to spot any oil or fuel leaks that might be developing in the engine compartment so that they could be repaired before catastrophe could strike. In reality, on average, crop dusters wash on a weekly basis but, there is a wide variety of philosophy on aircraft washing.

The dangers of working around crop duster chemicals

The working life of an aircraft technician is not inherently dangerous overall. Spinning propellers, liquid oxygen, high pressure hydraulic systems, high voltage ignitors, sharp aluminum panels, heavy starter generators, high platforms, bad pilots, etc. are all some of the dangers that a technician is exposed to.

However, if you are faced with performing maintenance and repairs to agricultural aircraft, your occupational risk is increased.

As if exposure to methyl ethyl ketone, zinc chromate, jet fuel and many other chemicals are not enough, now you are dealing with agricultural chemicals as well — some of which can be deadly to you, if you do not know how to handle yourself around them. Usually agricultural aircraft carry and dispense four different groups of chemicals. These are insecticides, herbicides, fungicides, and fertilizers.

By the way, fertilizers are the worst source of corrosion. If you know that the aircraft is in contact with a lot of fertilizers (especially powder-type fertilizers that become airborne), you should make a note of it and conduct a much more detailed inspection on the aircraft.

How can you best protect yourself against these harmful chemicals? First of all, it's best not to deal with them at all. If the aircraft looks dirty, don't deal with it.

But if you insist, you've got to do a thorough cleaning of the aircraft before working on it while also complying with all EPA and OSHA regulations. The operator is certified to work with these chemicals, so it's really best to let him do that.

Again, regular inspection of the aircraft is the very best defense against any major problems developing in the future. When an Ag operation is run correctly, a phenomenal amount of wastewater is accumulated. Safe disposal of this water is very important. Usually the aircraft washing area is designed to catch and collect the waste, which can then be pumped into waste disposal containers or recycled as make-up water for a new chemical batch.

If you handle the AG chemical waste in the same way as you do with normal aircraft paint stripping waste, you normally can't go wrong. However, always make sure that any clothes that you have worn to work on an Ag aircraft are washed separately from the rest of your laundry, so as to guard against any contamination of other clothing.

It is always recommended to rinse any items that have come into contact with any Ag chemicals, at least three times before re-use. Please observe this triple-rinse rule at all times. The EPA uses this "triple-rinse" as a standard for de-contamination of containers. When a container has been "triple-rinsed," it can then be recycled as a "de-contaminated" container.

When dealing with a tubular steel framed structure, annual inspection of the tubes with a fabric tester is prudent. Any time the interior of the steel tube is corroded, the fabric tested will indent the tube and you will hear the rust become dislodged. If the tubular structure has small access holes, (sometimes filled with a small rivet), you should coat the inside of the tubes with warm linseed oil or a suitable corrosion protection compound. Drain off the excess and then reinstall the plug rivet. The linseed oil provides a suitable barrier against corrosion occurring internally within the tube.

With aluminum monocoque structure, a regular coating of corrosion inhibitors is also good practice. But, in this instance, be very careful to observe if the corrosion protective solution, which turns to a very thin waxy film, does not become contaminated with Ag chemicals during flight operations. Fresh water, a good acid free detergent soap, a brush, dry towels, and a good polish are the best tools in an Ag technician's armory against corrosion.

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