Cleaner/degreaser caused corrosion

[SASless]

While trading cornbread recipes and sipping some Rootbeer....a former US Coast Guardsman reported the Hooligan Navy has banned certain "green" and "orange citrus" household detergents after discovering significant corrosion and similar degradation of aircraft skins and airframes.

He suggested the cleaners found their way into cracks, crevices, and joints on the aircraft and over time "ate away" metal in those confined spaces.

Anyone heard of similar problems?

[cpt]

Years ago, 2 or 3 Alouettes 2 suffered a rotor hub breaking. All of these had previously been operated from tuna fishing boats. It has been said that the cause of this rupture had been the use of an unapproved grease having deteriorated a varnish protection coating, thus allowing corrosion to settle on the rotor hub.
But the grease didn't actually corrode the metal by itself.
I haven't heard of any other case of rotor hub breaking on this type of helicopter.

[ericferret]

In the one case I know of the accident report said (from memory) that molybdenum disulphide grease had for enviromental reasons degraded into molybdic acid which had attacked the internal head parts leading to the loss of the main rotor.

Associated with this was the use of a commercial silicon sealer containing acetic acid
(vinegar smell) to seal the top of the head.

[bellsux]

I have known this for ages but over the years I have given up trying to convert others away from these degreasers. They are all highly alkaline chemicals and a good experiment is to drop a small piece of aluminium into some straight chemical degreaser and watch it start to fizz and corrode away. The only degreasers to use are the petroleum based liquids, may be a bit more expensive but they work better and don't cause corrosion.

[wrench1]

sasless,

Here's a quick link to some info. The US Army did a big study and the results are out there if want to look.

http://webmain02.fire.ca.gov/pubs/issuance/8300/Apa_004.PDF

W1