Corrosion: How does it affect the internal engine?

By Gary Schmidt Corrosion has long been recognized as one of the great enemies of the aircraft owner. Much has been said and written about corrosion in general aviation, but most of it pertains to airframe corrosion. Products and procedures have...

There is another little known product from Tanis Aircraft Services that is designed to deal with engine moisture and corrosion. It is a product patented by Peter Tanis to blow moist air out the inside of an aircraft engine. It connects to the oil breather tube and blows air through the engine out of the oil cap. It works best when the air inside the engine is warm and it has absorbed the moisture created by recent fuel combustion. The humid air is blown out and replaced with dryer outside air. If the outside air is cool, all the better. As it enters a warm engine, either warm by recent operation or warmed by a preheater, the cooler air will absorb more moisture as it warms. The use of the aerator is not recommended if the aircraft is stored in areas where the air is already very humid or where it may contain corrosive agents such as salt which is likely in some coastal regions.

Finally, when it comes to the inactive engine, the only course of action is to give your engine a "corrosion protection treatment." There are a variety of ways to "pickle" an engine such as Tanis Aircraft’s PIK-L-4 and PIK-L-6 kits for four- and six-cylinder engines.

At this point we should address another important misconception. Many have believed that ground running or even rotating the engine occasionally by hand would help protect the engine by distributing some oil through the engine. This is harmful to the engine. The pistons moving along the cylinder wall actually scrape the oil off the wall leaving it clean and susceptable to corrosive attack. Damage caused by scuffing the cylinder wall is also possible if pistons are moving in a cold engine. The fundemental purpose of preheating a cold engine is to bring the temperature of the metals (which contract in cold at different rates) to the point where they achieve acceptable tolerances.


Some may conclude after reading this that it is now all "clear as mud." As suggested at the beginning, this is not meant to be the final word on the subject. We are just collecting significant information already presented. Virtually all facts in this article originated from three basic sources: information published by engine manufacturers, Lycoming and Continental; data from the oil companies; and research by the late Peter Tanis of Tanis Aircraft Services Inc.

We have looked at the subject from a variety of angles and in spite of the uncertainty of some facts, it appears we can safely conclude the following: Damage from corrosion is a serious problem and deserves every general aviation aircraft owner’s attention. Further, even if we do not all clearly agree on the causes, steps can be taken to minimize the effects of corrosion by the way we fly and how often we fly the aircraft. Or, if we don’t fly often, giving our expensive power plant a corrosion protection treatment.

About the author

Gary Schmidt recently purchased Tanis Aircraft Services. You can contact Gary at (320) 634-4773 or by e-mail at

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