About 20 years ago I was looking for a readily available product which would slow corrosion in the steel firearm sound moderators (silencers) which we had just started importing from Finland to the UK. I tested various products which the average rifleman would either have in his garage or gunroom, or could reasonably add to the weekly supermarket shopping list.
The “test” consisted of taking a few steel plates (EN 8, IIRC), spraying or daubing them with various types and grades of oil, and leaving them in a Scottish farmyard for a few weeks. Somewhat surprisingly, the most effective product by far was WD-40.
I didn’t try ACF-50 or any of the “advanced” anti-corrosion products, because I was looking for something which the most idle of our esteemed end-users could ask his wife or girlfriend to pick up in Tesco without risking a rolling-pin accident. 
In my test, the WD-40 plate appeared completely devoid of oil within a day or so and I assumed that the rain had washed it off but after a couple more weeks it was still corrosion-free.
The conclusion which I drew was that “anti-corrosion additives” peddled by Shell, Total, Camguard et al. are not just marketing snake oil, and that they do as much or more to protect bare steel than mere viscosity.
My home built engine dehumidifier used a 240 volt aquarium air pump, a Wi-Fi switch and a 4G network dongle so I could monitor humidity, set timers and turn it on an off at home using an app! I made it as my aircraft went in for a respray and wing spar work for 3 months. I got the engine humidity down to 8% and I could tell when the paint shop had unplugged in by mistake. The first time I phoned then to tell them to plug it in again, they were quite spooked/ impressed in equal measure!
I need to rebuild my device for 12 volt/solar use in case we have a long lock down. My 240 volt, 4 watt pump delivered 0.016MPa @ 4 litres per minute and struggled with thin tubes, it only started working properly with 16mm OD tube.
I’m looking on Amazon and Ebay for solar pumps (or 12 volt pumps) but most look a very under powered. Any recommendations welcome but I think what is important is the pressure a pump can deliver, not the flow rate.
@Archer-181,
That sounds an interesting “lockdown” project, and if you could spare time to share details of your system (diagrams, photos, products, suppliers) it would save others re-inventing it.
So as there is quite a bit of resistance pushing the air past the beads of Silica Gel, I wonder if something like this which looks like it has a little piston would do a better job running 6 minutes per hour hour to consume 35 watts x 0.1 hour =3.5 watts per hour, rather than a 4 watt pump running all of the time.
This has a proper brass nozzle and looks like it could develop some pressure. The dry air in the crankcase every hour would still dry thinks out?
https://www.diy.com/departments/unibond-aero-360-moisture-trap/307283_BQ.prd
I keep 3 of these in the aircraft cabin all year round and really rate them.
My plan is to put a pump in a large plastic box with 3 more of these in the box, all sealed up except for the tiny air inlet, and a hole for the outlet pipe/hose.
Add a battery, timer and solar panel.
Archer-181 wrote:
My 240 volt, 4 watt pump delivered 0.016MPa @ 4 litres per minute and struggled with thin tubes, it only started working properly with 16mm OD tube.
At these pressures, why would the diameter of the tube matter at all? TBH, I was wondering on how much the silca beads in the 70cm tall contraption restrict air flow… A good use for the pressure section of the BMP280 sensor, perhaps, so see how long it will take for pressure to build up with a plugged exit tube.
There will be a direct tradeoff between the volume (or mass) or air pushed through the silica gel, and how dry it gets.
When I was experimenting with this a few years ago I decided that a good working device can be constructed with a tiny 5V fan which would run off a small battery for about a week. The amount of air pushed through the 0.5kg silica gel bag would be very small, but there is no need for a high flow rate – because you have lots and lots of time. If it takes a whole day to displace the humid air inside the engine, that’s just fine. And it will take a long time because it has to be pushed past the piston rings and then past the valves which may not actually be open (or the other way round if pushing the dry air up the exhaust pipe).
I would be cautious with the B&Q product above. The liquid is a concentrated salt solution. One spill of that in an airframe will negate decades of trying to keep it dry.
Fine for an RV or boat, no thank you in an aircraft. I was less forceful with my view in a group I was part of, everyone insisted they would be careful. It wasn’t a month before it spilled on part of the leather interior, destroying it. Thankfully it didn’t seem to get on or in the aluminum structure.
I would stick with silica beads.
The aircraft is unfortunately parked outside at a grass strip.
I can’t imagine how many kilos of beads you would need to produce the equivalent result.
As a point of reference someone who was doing it that way reported hugely different results when switching to one of those.
I agree that there is a risk, and care is of upmost importance. I’ve been doing it for 3 years with no scare stories yet.
Cumulatively between the 3 units I have, it’s commonly collecting about 1/2 a litre a week.
If anyone can suggest a way to keep up with that
outside of a hangar, with no mains power, I’d be interested.
There are good data points for silica gel in the cockpit here and I would think the engine is much less of a challenge, because if you blow dry air up the exhaust pipe, or up the crankcase breather, it will end up all around the inside of the engine, and the volume is pretty small.
In comparison, the cockpit is large and has loads of leaks.
