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Old 19th Mar 2017, 11:18
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westhawk
 
Join Date: Jun 2005
Location: USA
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A short summary on corrosion control based upon my own experience and schooling:

For effective corrosion protection, any accumulated salt should be removed as soon as practical following flight. This is best accomplished by flushing all exterior areas of the aircraft with clear fresh water. Protect air data probes and other water-sensitive components I/A/W the MM instructions regarding aircraft washing prior to flushing. Dry the aircraft. That takes care of removing salt from the aircraft exterior.

The importance of salt removal cannot be overstated. In aluminum skinned aircraft left with salt on the metallic surfaces and fasteners, salty water is an almost ideal electrolyte for several types of electrolytic corrosion, particularly where dissimilar metals interface and between faying surfaces like lap joints. (remember the Aloha Airlines pop-top 737?) Corrosion cells can grow very quickly and cause severe damage in a relatively short time.

Removal of salts from the equation drastically reduces the speed at which corrosion oxidizes the materials. Nothing stops corrosion entirely. Even the most vigilant care and the most advanced protection materials cannot stop it entirely. At best, the rate can be slowed to an acceptable level. NASA, the US Navy and numerous other agencies and universities around the globe have published scads of scientific studies while manufacturers have invested heavily in developing materials and practices to reduce the impact of corrosion on the useful life of aircraft structures.

One critical aspect of corrosion control is regular inspection of protective surfaces like the paint and any sealing compounds. This applies to airframes and engines as well as all their respective components likely to be exposed to salt water incursion. Any breaches of protective surfaces should be inspected for developing corrosion and repaired in a timely manner before restoring the protective surface to a state of effectiveness.

Turbine engines may require more frequent compressor washes, depending on exposure level. Seaplanes operating on saltwater and certain offshore helicopter ops may require hours of corrosion mitigation work each day between rinsing, inspection and any necessary protective compound application. The bottom line is that salt removal and protection application when operating in a saltwater environment is a daily activity in most conscientiously run operations. The frequency of inspection and lubrication activities on the whole aircraft and most of it's components must be increased according the frequency and intensity of salt exposure. The inspection schedule approved for the airplane becomes entirely insufficient in a high salts operating environment.

The application of corrosion protective compounds is widely considered to be most effective when applied to clean, dry and salt-free surfaces. But that has never stopped operators from looking for shortcuts! And it usually costs them much more in due time. Use only manufacturer approved protective materials, or risk doing more damage than you prevent.

I just had to comment on this subject too.
Don't use petroleum based products to clean canon-type electrical plug connectors without manufacturer approval. Some of them eat the sealing and/or insulating material inside the plug. There are specifically designed and approved products for cleaning the connector pins and receptacles, both mechanical and chemical.

Last edited by westhawk; 19th Mar 2017 at 19:32. Reason: correcting a word usage error (fatigue can be as bad as alcohol impairment!)
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