Engine corrosion at temps below -13 F (-25 C )

Hi guys,

I’ve been doing some reading and have found a few sources that say corrosion is negligible below the freezing point.
If my plane sits outside at -13 F for longer than lycoming’s suggested 30 days between flights in your opinion will this be cause for alarm?

Thanks for your input

I would think you're good to go as long as the case is purged after the last flight while still warm

The colder it gets the less moister the air can hold so as long as your engine is dry right now I’d say little to no chance of corrosion in those cold temperatures.

I’d guess it is more related to chemical reaction rate as a function of temperature than to moisture in the air. Both influence corrosion (oxidation/Chemical reaction) rate. There are famous stories about discovering WWII aircraft that had crash landed on glaciers or similar environments. They spend decades there and we’re eventually under meters of ice. Once excavated, the efforts to get them flyable we’re surprising quick and simple.

The comment about the engine internals is correct. It is a swamp in there after operation.


Hopefully a ChemE will reply with a graph showing the contributions of each; dew point and temp.

I would be shocked if more than a negligible number of engines get the "preservation" between non use that Lycoming recommends. This is not to speak ill of the recommendations, but rather on the deaf ears. I am sure most is not intentional, but look at the number of airplanes that sit for more than 30 days without even a consideration for the engine. I would not think that it happens within the forum, as most here are well above average caretakers. I cringe at all the airplanes I see at my home port that haven't moved in years...

Freemasm said:

...
Hopefully a ChemE will reply with a graph showing the contributions of each; dew point and temp.

Click to expand...

Here are some graphs:

https://www.engineeringtoolbox.com/moisture-holding-capacity-air-d_281.html

Seems like very cold air does not hold much moisture.

Interesting read…

I haven’t read it all yet, but according to this paper there is definitely a correlation between temperature and corrosion.

https://www.researchgate.net/profil...limate-a-review.pdf?origin=publication_detail

poorly worded, sorry

Hopefully a ChemE will reply with a graph showing the contributions of each; dew point and temp.

I didn't mean the relationship between the two. I meant the individual contributions of each related to the chemical reaction.

Water content in air (humidity) is limited by temperature but positively related; higher temp ->higher possible humidity.

Reaction (in this case corrosion) rates are a function of temp; also positively related.

Was hoping a ChemE or Chemist could show the relative contributions of each.

Ambient moisture in the air is a negligible problem, especially in cold temps, compared to the moisture that accumulates in the crankcase from condensation, and that's going to occur every time the air in the crankcase cools to the dew point. Those mornings where you come out to fly and find frost or dew on the wings?....same thing has likely happened inside the crankcase.

Two ways to keep condensation from happening...either keep the crankcase temps above the dew point at all times, or keep the humidity of the air in the crankcase low.

Freemasm said:

Hopefully a ChemE will reply with a graph showing the contributions of each; dew point and temp.

I didn't mean the relationship between the two. I meant the individual contributions of each related to the chemical reaction.

Water content in air (humidity) is limited by temperature but positively related; higher temp ->higher possible humidity.

Reaction (in this case corrosion) rates are a function of temp; also positively related.

Was hoping a ChemE or Chemist could show the relative contributions of each.

Click to expand...

I’ve learned quite a bit about corrosion from the paper I linked.

TOW = time of wetness

“ The main factors determining the level of corrosivity of an open atmosphere are the TOW, air temperature, relative humidity and the concentration of contam- inants (sulfides in industrial regions and chlorides in coastal regions). The effect of the first three factors can be taken into account using a generalized characteristic called the temperature–humidity complex (THC), which is defined as the duration of exposure to a certain combination of air humidity and temperature.”

Basically, for the next couple months in -25 C temperatures in my geographic location my aircraft should experience close to zero corrosion on exposed bare metal.