Aluminum & Steel Trailer Parts- Dissimilar metals?

[drams_1999]

So I am calling on the other engineers in this forum for their knowledge regarding dissimilar metals. I have an Aluminum trailer with my "M" and have dropped the steel axle so I can clean it and apply ZRC Cold Galvanizing to it. My question is: Do I need to do worry about aluminum and steel reacting (i.e. as dissimilar metals) with each other at points of contact?

Whatever was between them originally seems to have decayed to dust and I was wondering if I need to isolate the steel from the aluminum. I'm not sure if they react to each other over time.

Your thoughts, as always, are appreciated!

Fair winds!

[raycarlson]

I just spray a coat of rustoleum metal primer at contact points and that solves the problem. at points with galvanized steel its not steel its zinc that is making contact so corrosion is not quite as bad but I'd paint it anyway

[DaveB]

Metals like stainless steel. Zink coated or others connected to Aluminum and salt water will cause galvantic action.
Use nylon, Teflon,duron washers to separate the parts .
No spray paint will work.
Dave

[raycarlson]

Now yer tellin bs dave. rustoleum metal primer has worked just fine for six years now on my 08 alum M trailer, Maybe you used water colors or some other junk...lol

[mastreb]

Dissimilar metals will always corrode in contact, no solution prevents it, they're about slowing the process down to a point where the trailer will last its normal lifetime before corrosion failure becomes an issue.

The rustoleum rust converting primer, nylon washers, and all the other advice given work to do this, and you can do whatever will work best for you. I used tefl-gel on the mast parts for the same purpose, it's made for the purpose.

Any of these solutions are vastly better than doing nothing.

[BOAT]

Carbon Fiber Trailer?

[raycarlson]

Even carbon fiber when used in the aviation applications requires a double coat of primer where ever it will contact alum, steels, titanium the most common repair materials, not to mentions the poor characteristics it has when submerged in water with multiple fastener holes being soaked, so it is even a worse choice then alum with steel bolts, I've disassembled two of the original five prototype test 747s built in 1969 and even after 40 plus years a simple epoxy primer coat prevented galvanic corrosion between alum and steel parts, so applied properly I'll stick with that process as its simple and works well.

[drams_1999]

Thank you all for the advice!

I decided to put double coat of ZRC Cold Galvanizing on everything, with additional coats at the points of contact with aluminum and / or steel connection components.

I'll let you know if it holds up after a few more years of service.....thanks again for the advice!

[Hardcrab]

It's an electrical process doing the nasties to the different metals, so anything that keeps the two metals electrically isolated from each other is the goal.
Paint can be the perfect answer if you don't expect any flexing or relative movement to wear away the coating allowing the metals to electrically touch.
Nylon or some such harder non conductive substance if relative movement is expected.
(Even an electrical tape "gasket" can be very effective and long lived)

BUT, doing a great job insulating the big parts means nothing if the connecting bolts then blow it all by making an electrical connection as the assembly gets bolted together. Gotta keep those insulated as well.

If you know how to use an ohmmeter, test for infinite resistance between your axle and aluminum frame after you're done and know you have done the best preemptive job possible. The rest is up to the Corrosion Gods.

Then, take a sideways glance at the factory drawbar and think of the implications with the mild steel tube (sporting an unpainted interior), with SS bolts through the aluminum frame. (But take heart, I've managed infinte ohms drawbar to bolts, bolts to frame, frame to drawbar).

Good Luck

[mastreb]

Excellent idea using an ohmmeter to check. "Meggers" seem to no longer exist, so I guess you can't use those. They were hand-cranked dynamos that would generate electricity on one lead and check conductance on the other. They were specifically used to check for corrosion resistance by forcing a bit more power through the metal than an ohmmeter can muster with its battery.

I took some Whitney's frame rust converter with a long spray hose to the interior of my drawbar when it was a few months old, and that has worked wonders to prevent rust. Just snake it in, spray while you pull out, and done.

Everything I didn't rust convert, like the stock jack and the safety cables, are rusted to useless now.

[EZ]

Excellent idea using an ohmmeter to check. "Meggers" seem to no longer exist, so I guess you can't use those. They were hand-cranked dynamos that would generate electricity on one lead and check conductance on the other. They were specifically used to check for corrosion resistance by forcing a bit more power through the metal than an ohmmeter can muster with its battery.

I took some Whitney's frame rust converter with a long spray hose to the interior of my drawbar when it was a few months old, and that has worked wonders to prevent rust. Just snake it in, spray while you pull out, and done.

Everything I didn't rust convert, like the stock jack and the safety cables, are rusted to useless now.

I used Eastwood frame rust converter on the inside of my drawbar. I think mastreb was the one who recommended it to me.