Aluminium rear bumper beam - Galvanic corrosion?
 

Having bumpers and trims all off the car at the moment, I'm coming across a few little corrosion issues.

See images attached of the rear bumper beam (removed from my car) - it's got some oxidisation around the bolt holes - presumably galvanic corrosion from where it's been touching the steel bolts?

Now, the corrosion isn't bad. But, is there an easy fix for this type of thing?

The only other place I've seen this on the car is where the aluminium part of the rear window seals touches the steel of the rear quarter-light upright (and turns most of the aluminium/seal to mush) :(

I'm thinking of lining all such areas/bolts with a good smear of red rubber grease (which is nice and tacky).


Cheers,
Karl.

The easiest thing is to make sure there is no physical contact between the 2 different types of metal; something that coats it and stays there - I would say a very tough paint if it would stay in place; Hammerite?

Bolts/studs labbered in WaxOyl will fix it.


TC

We have assemblies at work on our trains which are dissimilar metals and we use a non-chromate jointing compound between them to prevent electrolytic corrosion - i'm surprised the MGR never did originally.

In the case of steel vs aluminium, the ally is the sacrificial anode and so will dissolve and leave the steel untouched. I'd suggest probably getting a replacement crash beam and then using the compound between them.

I have seen in the past, barrier tape between mating faces, so you could use duct tape or similar.

https://shop4fasteners.co.uk/duralac...iABEgKaRPD_BwE

I use ACF50 products on dissimilar metals. They use it on aircraft carriers so it must be good. I've found it on Ebay in the past.
http://www.acf-50.co.uk/corrosion_block.htm
Also comes in spray cans. Don't spray anywhere near brake discs though. It does not help braking (as a mate found on his GSF600)!;)
I have a spare rear beam from a low miles 05 car if you want one? Going for scrap soon if not?

You could always fit Nylon washers, or even fibre washers to the bolts & paper gasket between the crash bar and the chassis arms.

Red Rubber grease used to be Hydroscopic , if it still is, it will absorb water not repel it.

Very kind of you to offer, Mike - thank you.

But no need, I've got a good one to go on (and will keep the old one for spare) :)


Cheers,
Karl.

Thanks for the info Derek.

I've actually no idea of the hydroscopic properties or otherwise of red rubber grease :shrug:

But I've had good results with the stuff I've used in the past, so don't have any worries in this regard.


Cheers,
Karl.