The International Cessna^® 170 Association

Corrosion , no mater how minor I get a sick feeling in my stomach when ever I find any. While crawling around the back of 84A I noticed that the rear door post fairings were corroded where they were rubbing on the fabric of the side panels (both left and right). I removed the fairings and was relieved to find that there was none of that insidious airplane eater in the door posts. The fairings look easy enough to fabricate, but I am curious about the cause of the corrosion in the first place. Maybe a previous owner used a solvent on the fabric and that caused the corrosion. Has any one else seen anything similar? The rest of the airplane is relatively corrosion free, the prebuy back in May with me poking and prying with mirror and flashlight did not turn up anything.
I have been kicking around the idea of new paint and interior, even though I could probably get a couple more years out of it. This may have made my mind up!
Thanks,
David A.
9584A

David,
I think the word corrosion strikes the fear of God in just about every plane owner. We are on the coast down here in south Texas, and probably live in one of the most corrosive environments in the nation. Corrosion will creep in anywhere the paint or primer (if painted), has not adhered to the surface. If a screw is taken off and put back on, it may break that bond and bang, corrosion. If the paint is worn away, corrosion. If the surface is not properly cleaned and prepped before primer or paint is put on, corrosion. If you are going to just touch up the area you have problems with, just remember you must have a good adhesion between the paint and the surface. Acid etch and alodine is a must after COMPLETELY removing the corrosion. If you leave ANY, you are waisting your time. We are in the process of rebuilding a 53 model and have run into not only surface corrosion, but intergranular corrosion on some parts. make sure the metal is "white" when you have cleaned it, then acid etch, alodine, prime and paint. US Paint makes a primer specifically for fighting corrosion on aircraft. The Navy and the Coast guard use it, and it works well. After you have painted, a good corrosion fighting chemical such as corrosion x etc., can be used to protect even the bare metal in your plane. I have been told by some individuals that you must not use these chemicals on a freshly painted aircraft because they will cause the paint to blister or raise, (especially around the seems). let the paint cure for a while before applying these chemicals and they work great. They have done this, so I know that problem may exist if you dont give the paint a chance to cure. You can put plastic washers under screws and bolts that are non-structural, and that will protect against breaking the paint surface, and keep a good coat of wax on all the surfaces.
Just some of the experiences I have had with corrosion. Good luck,
Jon

David, what indicator of corrosion did you find? If you only found a white powder, it's possible you were observing mold or fungus spores (usually caused by previously trapped moisture or humidity.)
Was the metal actually pitted and/or eaten away? Or were you simply seeing white-colored powder from abrasion between the two? Vibration against the metal doorpost can cause the fabric threads to deteriorate into that which resembles corrosion where none actually exists.

George, sorry I didn't answer your response earlier, took the wife and kids to Burnet and Marble Falls for New Years (wanted to see what I had missed from the X-mas party). The corrosion is on the interior rear door post fairings, the metal is actually eaten away and crumbly from where they were rubbing the fabric. Luckily, everything else looks great and is corrosion free, even the fabric looks good. I just thought it was an odd place for corrosion citing the lack of corrosion in other areas.
David
9584A

I wonder if that fabric has a chance to soak up water or if it's been treated with something corrosive. Any other locations that fabric is in contact with metal?