The chemistry behind this and the practical use of SS fasteners confirms that aluminium fastened with SS fasteners is a good choice.

To further complicate things, SS fasteners are often not a good idea in... stainless steel!

If it offers you any comfort I have used SS fasteners all over my LR including direct contact to aluminium - been there for about 5 years now... no issues with corrosion.

When it comes to metals the best combination would be to use the same metal for everything, not just the same type of metal, but the same exact material specification - which you will never get as sheet steel and bolt steel for example are different grades!

Until you crash and your vehicle falls to bits, stainless isn't as good a fastener as steel for a number of reasons, its brittle for a start.
 
And I thought I was being cautious! Love the attention to detail. On my little repair job I'm going to great lengths to isolate steel from stainless from alu. Im feeling like a part timer compared to complete chassis isolation :)

I just used nylon/plastic washers when I did mine, 12 years on its still fine, but then again it took over 20 years to corrode in the first place, 12 years on and ally corrosion is the least of my worries.
 
Would a CSD disc be a good choice to grind down the aluminium corrosion?

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I put insulation tape between dissimilar metals and use regular zinc plated fixings . I was going to write it isn't rocket science at the end of this sentence, but maybe it is !
 
This was mine after the first time I jet washed the underside after getting in in January 2009, and then again nearly nine years later when I finally got round to patching it a month ago....

Oh how I wish I had treated the underside rather than just talking about it, its a 52 plate btw.

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This was mine after the first time I jet washed the underside after getting in in January 2009, and then again nearly nine years later when I finally got round to patching it a month ago....

Oh how I wish I had treated the underside rather than just talking about it, its a 52 plate btw.

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Oh man I feel for you... I'm also impressed with your repair - respect.

I have cleaned mine off and used etching primer followed by a couple of coats of paint on the new aluminium patch panels and the area being patched. I will sikafex/rivet the panels in place this week. The steel will be separated from the aluminium by a butyl patch and insulating tape on the stainless bolts. There will be a lot of greasy gunk applied on the underside to keep it all as dry as it can be.
 
Wow, that's some serious corrosion. And really hard to stop because because of the direct connection with the body crossmember. Hard to believe they still built cars like that till 2014! ;-)

Mine looks like this. A lot better but I still need rivet on a repair patch.

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I tried the CSD disc to remove all the corrosion on the surface and the result looks pretty neat. Bare metal without without too much damage or thinning.

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So my little repair is coming along nicely. I went low tech and scrapped, brushed and manually sanded the affected bits of the landy back to good metal. The three aluminium patch panels have been primed and painted, as have the affected areas of the landy. Patches now installed with sikaflex and rivets. The rivets are probably not necessary but better safe than sorry.

The underside has had the waxoyl cleaned off, primed and painted. I had some self adhesive semi-solid sound deadening material and so I have attached that to separate the aluminium body from the chassis seat mounts. It also forms a tight seal around the holes in the body once the bolts are in place.
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. I've also put some butyl putty where the rivets poke through on the underside. It will all get a coat of waxoyl when the underside gets its winter top up in a few weeks.
 
I tried the CSD disc to remove all the corrosion on the surface and the result looks pretty neat. Bare metal without without too much damage or thinning.

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That's only down to bare metal in parts. There's still some pitting on the surface with oxide in it and the holes themselves are untouched. Ideally all of that oxide needs to be back to bare metal, both surfaces and the inside of the hole.
 
Yeah, I know about the holes, I did that with sand paper afterwards. My test was more about flat surfaces. That's normally what you can do with an angle grinder.
 
I work in the marine industry some of the time. When aluminium or alloy fittings are bedded together in the salty environment (electrolysis can be rampant!) the industry standard compound is Duralac. https://www.force4.co.uk/duralac-anti-corrosive-jointing-compound.html#.WdWdFkHTX7o Other suppliers available and I've no connection with Force Four: it just happened to be the first Google hit I copied.

It's also used (or something very similar) in the aircraft industry when joining aluminium and other metals together.

I'm surprised no one seems to be aware of it when rebuilding or repairing Landrovers?
 
I work in the marine industry some of the time. When aluminium or alloy fittings are bedded together in the salty environment (electrolysis can be rampant!) the industry standard compound is Duralac. https://www.force4.co.uk/duralac-anti-corrosive-jointing-compound.html#.WdWdFkHTX7o Other suppliers available and I've no connection with Force Four: it just happened to be the first Google hit I copied.

What is it? ^^

I mean is it a grease, something chemical, a metal coating?!
 
It's the trade name for Barium Chromate paste. It's a gloopy thick yellow grease like substance that forms a barrier between the metal surfaces. It dries after a while. For more details see http://www.llewellyn-ryland.co.uk/downloads/duralac.pdf

I've no connection with the manufacturer or suppliers but I was surprised that I've never seen it mentioned in Land Rover rebuild accounts as it's use is extremely common in the marine industry that faces even bigger challenges over aluminium alloys and galvanic corrosion.
 
I work in the marine industry some of the time. When aluminium or alloy fittings are bedded together in the salty environment (electrolysis can be rampant!) the industry standard compound is Duralac. https://www.force4.co.uk/duralac-anti-corrosive-jointing-compound.html#.WdWdFkHTX7o Other suppliers available and I've no connection with Force Four: it just happened to be the first Google hit I copied.

It's also used (or something very similar) in the aircraft industry when joining aluminium and other metals together.

I'm surprised no one seems to be aware of it when rebuilding or repairing Landrovers?
Nope, never heard of that, but it'll be on the shopping list no doubt. Cheers. :)
 

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