Aluminum Tubs & Dissimilar Metal Corrosion (1 Viewer)

[Fadiddy]

Sup guys,

For those of you who have aluminum tubs, what have you done to rectify the issue with dissimilar metal contacting? I know some have stated NOT to mount any grounding points on the aluminum tub and to do so directly on the chassis....but, what about things like engine bay accessories (i.e., igniters, etc...) that are normally mounted on the body? Will I have to ground those down to the chassis as well?

Thanks.

 

[jm599]

I haven’t had problem, use stainless hardware and ground body to chassis too.
Finished mine ‘06,
Seal connections with black silicone

 

[jim land]

You can use a bus bar like on a glass body.
I dont know why you cant ground direct on the alu tub .

 

[4x4veteran]

Moisture getting in the aluminum and steel works as an electrolyte causing the corrosion.
Not saying it can't happen but I have never had any problems with aluminum on steel body parts but have had to nearly destroy a couple of alloy rims stuck to the hubs of a car.
If you need a ground through the aluminum and can't seal it then keep it dry and inspect every once in a while.
I have never had an aluminum bodied car but have had clean grounds on steel so if you keep the spots clean and seal them like jm599 suggests it shouldn't be any worse than any other connection.

 

[Cat Scan]

Others may have mentioned this but you are discussing Galvanic Corrosion Prevention / Dissimilar Metal Corrosion. There are tons of articles on line regarding this issue. There are also products for coating fasteners that are helpful. ECK is one of them. It is available at Amazon. The marine guys utilizing stainless steel fasteners on aluminum boats have had to deal with this issue. Depends on the size of the item you anticipate touching the aluminum tub. Some paints are suggested for this purpose, others have utilized neoprene between the two surfaces. Hope this helps. Good luck!

 

[Fadiddy]

I like the idea of the bus bar @jim land suggested.

So, the corrosion doesn't necessary happen at all the fastener points of the aluminum part to steel part contact points, it's only where there is moisture and electricity running in between the two parts? In other words, other stainless steel fasteners around the body outside or inside wouldn't necessarily corrode even though there are electrical components grounding to the body?

Sorry to sound remedial at this...I'm fairly proficient in automotive electronics, but this dissimilar metals area is new territory for me.

 

[fjc-man]

How about a smear of NOALOX on what ever ground connector you are connecting to the aluminum tub?

 

[billmc]

I like the idea of the bus bar @jim land suggested.

So, the corrosion doesn't necessary happen at all the fastener points of the aluminum part to steel part contact points, it's only where there is moisture and electricity running in between the two parts? In other words, other stainless steel fasteners around the body outside or inside wouldn't necessarily corrode even though there are electrical components grounding to the body?

Sorry to sound remedial at this...I'm fairly proficient in automotive electronics, but this dissimilar metals area is new territory for me.

Well, the s/s bolts won't corrode, but the capture nuts in the body sure will, especially if they're aluminum. Stainless is much higher on the galvanic scale the aluminum or iron for tha matter (as are nickel and chromium). And no you don't need explicit electric current to have the reaction occur, just electrolytes in solution (ie, any road spray)

 

[Splangy]

I see no reason to avoid using aluminum bodies as vehicle grounds. I would make sure you have redundant grounds to the chassis to avoid corrosion at the ground connections on the body (in the event of a poor connection in which water or soil can get inside of) but this is true with any metallic body.

While coupling metals of differing potentials should normally be avoided to prevent corrosion, just looking at the placement of aluminum and stainless steel in the galvanic series is overly simplistic. Stainless steel fasteners can successfully be used with aluminum components in mild environments without significant corrosion to the aluminum. When coupled together, the stainless steel will cathodically polarize (assume a potential closer to that of the aluminum), reducing the corrosion In the galvanic coupling.

I would choose stainless over any carbon steel fastener (zinc plated or otherwise) if you want to prevent/reduce corrosion of the aluminum.

 

[White Stripe]

Aqualu knows a lot about this if you call and ask them.