Can engine heater reduce/prevent engine corrosion?

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MountainDude

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MountainDude
My first year in Seattle with a hangared C182, with an O-470.
I have a very nice engine heater that heats each cylinder and the oil pan.
Given that humidity will be >90% for the next 6-7 months, and that I may not fly more than once a month (maybe even longer), I am worried about engine corrosion (the engine has 200 hrs on it).

Is there evidence that my engine heater can reduce or prevent the risk of engine corrosion?
Thank you
 
I think just the opposite...engine heater increases the temp changes that promote engine corrosion unless you keep it running 24/7/365 and keep the crankcase temps above the dew point. An engine dehydrator OTOH has been shown to decrease the amount of humidity in the crankcase and upper engine. If you might think that increased humidity in the engine might contribute to corrosion in the upper engine then you'd want a dehydrator, not a 24/7/265 heater.

https://www.aviationconsumer.com/maintenance/engine-dehydrators-engine-saver-prevails/
 
I don't have time to go to the airport frequently and replace the silica beads in a dehydrator.
Also, I "would" keep the engine heater plugged in 24/7 between flights.
I am hoping there are data on this, and not opinions or anecdotes.
Thank you
 
MountainDude said:
Agreed, but would the heater not prevent condensation inside the engine, so the overall effect is anti-corrosive? That is what I am thinking, but have zero evidence to back that up.
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Only if your heater schedule can keep the temps inside the crankcase above the dew point 24/7/365
 
MountainDude said:
Agreed, but would the heater not prevent condensation inside the engine, so the overall effect is anti-corrosive? That is what I am thinking, but have zero evidence to back that up.
Click to expand...
If the temperature is elevated above the vapor temp.....
 
This is a well discussed topic. The conventional wisdom is that leaving your heater on full time is bad for engines and bad for corrosion. Something like it’ll heat things up enough to pull moisture out of the oil, but not enough to evaporate it completely. I am not a scientist, but it goes something like that.

I like the dehydrator idea - seems reasonable - but short of that, a good engine heater and a remote switch (like a SwitchBox) is pretty much the gold standard short of a heated hangar. But those types of solutions are about cylinder damage and cold starts, not moisture and corrosion.
 
The simple answer is that heat accelerates corrosion. Condensation (dewpoint) isn’t a threshold for corrosion. In the presence of humidity heat will always accelerate corrosion. You’d be best served by parking in a deep freeze.
 
I disagree with several of the others. Keeping your engine above the dew point will keep the moisture from condensing on the inside of the engine and the will avoid corrosion. What will kill the engine quickly is cycling the heater like many do (e.g. putting on a timer or temperature switch). Cycling the heater causes condensation when the engine cools, and this will rot the insides. Tannis and Reif heaters do a great job of keeping the whole engine very warm.
 
What do the locals do? I don't think having months where you only fly once or even not at all is that much of a rarity. I would tend to think getting it up to full operating temperature and letting the oil coat everything internally once a month would probably be good enough but I've never lived in Seattle.
 
MonkeyClaw said:
I disagree with several of the others. Keeping your engine above the dew point will keep the moisture from condensing on the inside of the engine and the will avoid corrosion. What will kill the engine quickly is cycling the heater like many do (e.g. putting on a timer or temperature switch). Cycling the heater causes condensation when the engine cools, and this will rot the insides. Tannis and Reif heaters do a great job of keeping the whole engine very warm.
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Probably not much of an issue in Sedona. Big issue in Alaska. Somewhere in between in Seattle. Heat accelerates corrosion. Nobody ever qualified that it required liquid water. Humidity is all it takes. I have Reiff Turbo XP systems on both my airplanes. No way in hell would I leave them plugged in continuously.

To the OP, with respect to the question? Read what Continental as to say about it.

Do not leave an engine-mounted pre-heater system on for more than twenty- four hours prior to flight. Continuous operation of engine-mounted preheater systems may result in aggressive corrosive attack internal to the engine.

http://www.reiffpreheat.com/Continental SIL 03-1 Cold Wx Ops.pdf
 
@MountainDude Here's real data from Reiff, not anecdotal BS:
http://www.reiffpreheat.com/FAQ.htm#QA3

I leave mine plugged in 24/7 in the cold months. Like others have stated, it's the on/off cycles of the heater that cause damage and condensation. My rule of thumb is, if I'm going to unplug the heater, I'm going to fly. The heater will ALSO decrease humidity just like a dehumidifier will.

Edit: I do fly weekly and don't leave the plane unattended for more than a week.
 
Indeed. Corrosion is an electro-chemical reaction, and heat increases the rate of the chemical process. Also, realize that all of that chemistry can occur within a microscopic droplet of water that can settle on a metallic surface anywhere within the engine and begin to do its thing.
 
Every 10 deg C will accelerate chemical reactions by approximately a factor of about 2. So heating that is insufficient to completely drive out moisture will actually increase the rate of corrosion. The reason to warm your oil in the winter is to make it more convenient to start, and increase startup lubrication in cold weather.
 
Someone mentioned switchbox, it’s great for remotely starting the heater, unless you are flying don’t just switch it off. Out here everyone I know leave heater plugged in from mid nov to mar, unless they are not flying at all. I keep mine plugged in as well and fly once a week, but there has been situations where it has sat for 4 weeks with heater plugged in. Oil analysis haven’t showed any corrosion thus far. The worst thing you can do it switch on the heater for few hours, shut it off and don’t burn the moisture off. I also keep the oil dip stick unlatched with slight opening and I have a cool cover so that any moisture can potentially be escape and not form water droplets inside the tube. You will get all sorts of opinion including studies done by companies who have kept the heater plugged in all winter for several years and not showing anything other than normal corrosion.
 
Being in Western WA myself I would suggest talking to the locals on your field. I've seen planes with heaters that only turn on with an app when the owner commands it before a winter flight. I haven't seen dehumidifiers on planes at all but we did have them on our Abrams tanks in Yakima (eastern WA) and you could tell a difference between those that installed them properly and those that didn't but really only after months of no use, basically a non tank deployment..

Having a boat that sits in saltwater all year without moving for weeks at a time and an old pickup that does the same, I haven't really seen signs of damage during oil changes and an overhaul.

It is better to use it than to let it sit but I wonder if we don't do more harm trying to reduce damage. You know, the cure being worse than the disease.

I'd be happy to take one for the team and help keep your plane flying when you can't though. ;) I'm only partially joking... might even trade boat time for plane time. Just a thought.
 
MountainDude said:
My first year in Seattle with a hangared C182, with an O-470.
I have a very nice engine heater that heats each cylinder and the oil pan.
Given that humidity will be >90% for the next 6-7 months, and that I may not fly more than once a month (maybe even longer), I am worried about engine corrosion (the engine has 200 hrs on it).

Is there evidence that my engine heater can reduce or prevent the risk of engine corrosion?
Thank you
Click to expand...
The engine's purpose isn't to stop corrosion, it is to warm the engine for easier starts. then. you burn the water out.
 
Stewartb said:
Probably not much of an issue in Sedona. Big issue in Alaska. Somewhere in between in Seattle. Heat accelerates corrosion. Nobody ever qualified that it required liquid water. Humidity is all it takes. I have Reiff Turbo XP systems on both my airplanes. No way in hell would I leave them plugged in continuously.

To the OP, with respect to the question? Read what Continental as to say about it.

Do not leave an engine-mounted pre-heater system on for more than twenty- four hours prior to flight. Continuous operation of engine-mounted preheater systems may result in aggressive corrosive attack internal to the engine.

http://www.reiffpreheat.com/Continental SIL 03-1 Cold Wx Ops.pdf
Click to expand...

Wow! That is the best info I have seen so far. Thank you.
 
Mtns2Skies said:
@MountainDude Here's real data from Reiff, not anecdotal BS:
http://www.reiffpreheat.com/FAQ.htm#QA3

I leave mine plugged in 24/7 in the cold months. Like others have stated, it's the on/off cycles of the heater that cause damage and condensation. My rule of thumb is, if I'm going to unplug the heater, I'm going to fly. The heater will ALSO decrease humidity just like a dehumidifier will.

Edit: I do fly weekly and don't leave the plane unattended for more than a week.
Click to expand...

Wow, completely contradicting the post before the one, from the same website. :(
 
Unheated vehicles parked in Antarctica exhibit virtually no corrosion after many tens of years. OTH the relative humidity there is close to zero.
 
I notice the Reiff study was done in temps from 10 to 30F. That’s not the conditions you will see in SEA. I would go with the people who make the engines on this one.
 
Note, make sure you have an insulated prop cover on. Otherwise the prop acts like a heat (cold) sink and will cause your crankshaft to be colder than the rest of your engine. If that happens all of that moisture that's being pushed out of your oil will condense on your crankshaft.

I've been doing this for 3 years and get religious oil sample tests done and there are no changes from summer to winter. As the poster above noted I do this in temps below 40F which is where continental recommends preheat.

I'd rather get everything thoroughly heat soaked than plug it in an hour before flight and have some parts of the engine at wildly different temps. And I'm not going to drive to the airport just to plug in my heater.

Regardless of your method, these engines are more resilient than people on here give them credit for. You're not going to trash your engine one way or another, continentals in particular are far more corrosion resistant with the cam being underneath anyway.

The only way you can quickly trash an engine is by doing periodic ground runs without flying or improper use of a torpedo heater.
 
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To the point of engine resiliency, @Stewartb and I have the same plane and same engine. I'm a mechanical engineer, he has years and years of experience in Alaska. I think we disagree on nearly everything and yet my engine is 31 years old with 1000 hours and excellent compression and oil analysis (knock on wood). I'm sure his is doing just as well as mine despite our very different methods of care.

You will probably be fine no matter what you choose to do.
 
Having just bought my first airplane, which has a Tanis system, this is a timely thread.

Accepting that after you fly, there will be some water in the oil, and the air in the crankcase will be quite humid due to blow by. We don't know how humid, but it's probably enough that if the ambient temperature is below 50? 40? There will be some condensation. Thankfully at this point everything is still nice and oily. Now we are at 100% relative humidity. Further temperature drop results in more condensation, temperature increase will reduce the RH, but not the dewpoint.

The oil will eventually drip off the cam & other parts (but let's be honest, the cam is the one that we worry most about), leaving them unprotected. If the temperature stays steady, there shouldn't be any additional condensation. If it falls there will be. If we increase the temp., we cut the RH, but not the absolute humidity, nor the DP, so if the temp falls again the rh goes back up. The concern of many is that by heating the oil, we will drive some portion of the water in solution with the oil into the vapor phase, raising humidity. By warming the air in the engine, we reduce the RH (a 5deg. Temp. Increase cuts RH in half), making "room" for more water vapor. If the engine subsequently cools, BAM more condensation. It's these temperature swings that are the killer.

Anecdotal data time. My club has a warrior and a Dakota that were purchased new in the late 70's. Both these airplanes have had several engines, always with tanis heaters, always plugged in when the temp hits 50 or so and not unplugged unless flying or in the spring. Never has an engine failed to reach TBO+10%, which is when they are replaced as a liability concern. Now, the warrior has 14000hrs, and the dakota 10000, so they fly a lot, which probably has more to do with it than the heaters. It always amazes me though on a below freezing day how much warm air is rising out of the oil door when i go to unplug the heater. The club does not remove the dipstick, which i think is suboptimal, but it doesn't seem to have caused problems.

My plan is to run the heater all the time, but leave the dipstick out. My hope is that the warm, moist air in the cranckase will rise out the dipstick tube, and be replaced by low humidity ambient air through the crankcase vent. I suspect that after a few hours, the RH inside the crankcase will be too low to create condensation at any temperature. Even if the outside air were humid, raising its temperature 50deg will put the RH in the teens, and the metal parts of the engine will be well above the DP anyway.
 
The best way to prevent corrosion is to fly the airplane frequently. Even if you don't have somewhere to go, try to fly it every week, long enough to get the oil temperatures up. Oil additives such as Camguard may be helpful too. To answer to question, using an electric engine heater will not prevent corrosion.
Jon
 
Most of my opinion comes from having torn down engines and seeing what's inside. The balance is from watching others tear down engines. There is no question in science that heat accelerates corrosion. It applies to heated hangars, too. Leaving your engine in cold storage is better for it than heated storage. Heat reduces relative humidity but increases total humidity. With your heaters on you're making a greenhouse. Warm moist air rises and meets the coolest surface available. If you use a reiff system that'll be the top of the case, where it condenses and rains down to go through the cycle again. With oil pan heat and no cylinder heat? It'll condense in the heads. Pull the rocker drains on a Lycoming that operates in the cold and is kept warm in between flights. Heater or hangar won't matter. Tap the drains and watch the water come out. Personally I've been experimenting with inert gas purging of airplane engines for storage to reduce cam corrosion. Rust is oxidation. Removing oxygen is easier than removing water. With Continental's low cams argon seems to be the best choice. With Lycoming's high cam I'm using nitrogen. In both cases the gas flows out at the cylinders so that's the threshold level for the gas to remain. There's no practical way to seal the cylinders. I have more testing to do but there's promise.
 
MountainDude said:
My first year in Seattle with a hangared C182, with an O-470.
I have a very nice engine heater that heats each cylinder and the oil pan.
Given that humidity will be >90% for the next 6-7 months, and that I may not fly more than once a month (maybe even longer), I am worried about engine corrosion (the engine has 200 hrs on it).

Is there evidence that my engine heater can reduce or prevent the risk of engine corrosion?
Thank you
Click to expand...
Tanis recommends leaving the heather plugged in 24/7 in cooler weather, and I think that makes sense. Condensation stays on a surface when it's at or below the dewpoint, so if the OAT is 5c and your engine is at 20c, you should have much less issue with moisture on the metal.

Or, to put it another way, the amount of moisture in the air that causes 90% relative humidity at 5c will produce a much, much lower relative humidity if the air under your cowl blanket is at 20c. Either way, warm surfaces don't get wet in the winter.

Other advice, like Camguard, also makes sense. But whatever you do, don't buy one of those remote switches to turn your engine heater on and off -- every time it cools down, you'll be accumulating condensation on the surfaces. Keep it warm, like Tanis says to.
 
Stewartb said:
Most of my opinion comes from having torn down engines and seeing what's inside. The balance is from watching others tear down engines. There is no question in science that heat accelerates corrosion. It applies to heated hangars, too. Leaving your engine in cold storage is better for it than heated storage. Heat reduces relative humidity but increases total humidity. With your heaters on you're making a greenhouse. Warm moist air rises and meets the coolest surface available. If you use a reiff system that'll be the top of the case, where it condenses and rains down to go through the cycle again. With oil pan heat and no cylinder heat? It'll condense in the heads. Pull the rocker drains on a Lycoming that operates in the cold and is kept warm in between flights. Heater or hangar won't matter. Tap the drains and watch the water come out. Personally I've been experimenting with inert gas purging of airplane engines for storage to reduce cam corrosion. Rust is oxidation. Removing oxygen is easier than removing water. With Continental's low cams argon seems to be the best choice. With Lycoming's high cam I'm using nitrogen. In both cases the gas flows out at the cylinders so that's the threshold level for the gas to remain. There's no practical way to seal the cylinders. I have more testing to do but there's promise.
Click to expand...

I think you're on the right track. But... If you drive most of the moisture out of the engine after shut down, then keep the engine compartment warmer than the dew point, how do you get condensation? I'm not talking about keeping the engine 100+F, maybe 70F.

The purges (or floods) with inert gasses are interesting, but how do you seal up the engine well enough that you're not perpetually needing to pump more and more Argon, CO2, or Nitrogen in there?
 
kyleb said:
I think you're on the right track. But... If you drive most of the moisture out of the engine after shut down, then keep the engine compartment warmer than the dew point, how do you get condensation? I'm not talking about keeping the engine 100+F, maybe 70F.

The purges (or floods) with inert gasses are interesting, but how do you seal up the engine well enough that you're not perpetually needing to pump more and more Argon, CO2, or Nitrogen in there?
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I think if an engine were cold and stayed cold (e.g. in storage), the theory you're replying to would be correct. But when an engine keeps getting hot from flying (producing lots of moisture as a waste product) then cooling again, a cold surface will just attract all that moisture like a magnet, while a warmer one won't.

That should be familiar to anyone who lives in cold areas, like central Canada or the U.S. midwest -- the inside of car windows won't frost up when they're cold, or when they're warm, but when they cool after a drive back down to ambient temperature, that's when you get either fog or frost inside the windows. If you kept the inside of the car at 15 or 20c over the winter, the inside would never frost or fog up with low OATs.
 
kyleb said:
I think you're on the right track. But... If you drive most of the moisture out of the engine after shut down, then keep the engine compartment warmer than the dew point, how do you get condensation? I'm not talking about keeping the engine 100+F, maybe 70F.

The purges (or floods) with inert gasses are interesting, but how do you seal up the engine well enough that you're not perpetually needing to pump more and more Argon, CO2, or Nitrogen in there?
Click to expand...
When you raise temps you raise total humidity. Dew point goes up with it.

My gas experiment is only that. Trying to eliminate oxygen from the cam area. No oxygen, no rust. Heavier than air gas for Continentals and lighter than air gas for Lycomings. How gas purging lasts in a closed hangar environment is the unknown. I bought an oxygen detector and probe pump and already had nitrogen and argon tanks in the hangar. My first test was to pressure fill my Continental through the dipstick with argon and measure oxygen at the oil filler. It was alarming how quickly the gas exited through intake and exhaust. I hadn’t considered that. I need to fill a sealed engine and monitor oxygen below the cylinder level. Maybe this weekend, maybe not.
 
Another tip for you full time heater advocates. Don’t forget the constant speed prop hub. Internal AND external corrosion at the prop are very expensive to fix, and you’re setting yourselves up for it. Been there, done that.
 
Stewartb said:
When you raise temps you raise total humidity. Dew point goes up with it.
Click to expand...

No doubt. But if the external atmosphere is at (say) 40% RH and 30F, supporting 10G/M*3 of water, won't the internal atmosphere (assuming the crankcase is vented and warmer) move towards the same 10G/M*3, which would be lower RH?
 
The absolute best thing you can do for the engine is to fly the plane regularly and change the oil frequently. If you can't do that, consider giving access to the plane to a pilot that can exercise it regularly.
 
Stewartb said:
When you raise temps you raise total humidity. Dew point goes up with it.

My gas experiment is only that. Trying to eliminate oxygen from the cam area. No oxygen, no rust. Heavier than air gas for Continentals and lighter than air gas for Lycomings. How gas purging lasts in a closed hangar environment is the unknown. I bought an oxygen detector and probe pump and already had nitrogen and argon tanks in the hangar. My first test was to pressure fill my Continental through the dipstick with argon and measure oxygen at the oil filler. It was alarming how quickly the gas exited through intake and exhaust. I hadn’t considered that. I need to fill a sealed engine and monitor oxygen below the cylinder level. Maybe this weekend, maybe not.
Click to expand...
I'd love to know how to make that happen with my house in the winter. When it's below freezing outside and 21c inside, the dewpoint does not go up inside with the heat, and all our hands get dry and cracked. There needs to be a continually-replenished supply of moisture for the dewpoint to go up with the temperature. Even running big humidifiers in rooms with closed doors, it's an uphill battle to get the indoor relative humidity above 30% on a cold winter day.
 
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