Aluminium Corrosion on Stuctural Car Parts

[Broadsword]

The V70 needed some front suspension work on the nearside. Wheel bearing, lower balljoint and trackrod end. No problem. I started poking around and noticed the suspension leg (all aluminium) was like Swiss cheese in some critical areas under the mud. It looked a little frightening so I just changed the wheel bearing and returned to the job this week. Luckily the York U-Pullit is a few miles from where I live so I soon had the entire replacement suspension leg with a good balljoint and wheel bearing (leaving me with the new spare for the other side).

 

I think the problem here is Volvo mixing steel with aluminium. This is obviously galvanic corrosion (I am a chemist you know). So the question is that am I being paranoid as regard the degradation? The replacement leg is in far better condition so I'm happy with that now. Has anyone seen anything similar on their cars? Nothing on the MOT sheet about it but there was no way it would have been seen.

 

The pictures are after a couple of dead blows with a two pound hammer. A lot of crusty aluminium came off.

 

[Squire_Dawson]

I have seen it on the large hovercraft when delegates of the Solent shite contingent attended the excellent museum. Parts of the aluminium, particularly where it joined other sheets, was literally crumbling away, which struck me as quite a remarkable phenomenon. I suppose it must be brine and winter road grit doing it.

[MikeR]

 galvanic corrosion is very horrid  , also attacks  Range Rovers , the mixing of different metals is not a good idea for long time use , also thermal expansion ratios differ , ie alloy head on iron block gives the headgasket some work to do , so the more "fancy" a car , the more scope for issues ....  I have seen a grain of somat ( steel ? ) the size of a pin head burrow its way throu a Fiat alloy water pump housing , it left a wood worm like hole from the inside wall to the outside wall !

[danthecapriman]

I've seen similar on models before mainly on cast alloy chassis blocks. It happens when a contaminant is allowed into the mixture of ally/alloy and over time it reacts. It starts off as a bending of the casting but eventually gets so bad the casting literally just swells up and 'rots' and crumbles apart.

Apparently it's the contaminant reacting with the base material(s) and forces them to separate from one another. It can take years and years to happen but can be much quicker too. In model circles it's a known issue with certain manufacturers and known as Mazak rot.

[CreepingJesus]

We were talking about something similar on a Scottish Volvo page the other day: long and short is, TADTS. My V70 and 850 had, and Richard said something similar about his.

You might want to check your rear arms too: they're ally, and although the bushes and fasteners are quite well set up to minimise the electrolytic issues, it still can happen. And the arms can be quite soft if you're trying to batter one of the bushes out...!

[Pillock]

I had steel nuts in aluminium wheels on my Beetle. It took a scaffold bar to get those out, the wheels almost looked like they'd started to grow around the nuts!

[rantingYoof]

Is this what affects the Jaaaaaags that have aluminium bodies but steel tappets holding everything together?

 

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[Broadsword]

The situation at the rear is the opposite. The rear arms are perfect but the crossmembers to be centre of the car (steel) have heavy surface corrosion as actually do most of the steel bits. Worst on the shock absorbers (which I changed) and where part part of the rear spring snapped, but I haven't got around to changing that as it looks like a faff (good used spring waiting). The heat shield to the exhaust is ally and attached with rivets to the subframe. That all turned to dust when I prodded it.

[DodgeRover]

I've seen motorcycle wheels fail through it.

[CreepingJesus]

Seen similar on mine, yeah. The 'chassis legs' weren't pretty, but wire brush and Hammerite kept the worst in check. Good solid cars in the main, though.

[spartacus]

There's a similar issue on some Audi suspension components, I changed some on a car once years ago and had to do some careful drilling to get the bolts out, never again.

[dieselnutjob]

Is this what affects the Jaaaaaags that have aluminium bodies but steel tappets holding everything together?

 

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And I just fitted a towbar (steel) to mine (alu body)....

[Asimo]

The steel fasteners used with aluminium chassis components should be plated / coated to minimise corrosion issues. Trouble is of course that coatings can be damaged!

Just like good old ferrous rust, the secret of long life is to keep it all oily. This is the time of year to get brushing your favourite greasy goop all over those suspension parts, whatever metal or combination thereof they are made from, paying special attention to where steel and alloy meet.

I've been using Dynax thinned with WD40, 1/2 a car done, 2 1/2 left to do.

[Junkman]

I started poking around and noticed the suspension leg (all aluminium) was like Swiss cheese in some critical areas under the mud.

 

There should never be any mud on any suspension part, or the undercarriage, of a motor car.

It's even explicitly stated in many manuals, that if a car has been used in untoward environments,

it should be meticulously cleaned afterwards.

Now you found out why.

[DSdriver]

Duralac and Monel rivets

[MikeR]

all the underside of my 03 Focus is steel , and its surprisingly clean for its age , a wipe down with a cloth and a coat of fresh paint onto and into every bit of subframe and box section , followed up with a spray tin of oil into box sections and subframe inners ...  which does actually makes you wonder about mixing metals on a modern car as only troublesome bits have been where ally fastenings have been used on the underside .

 

 

 

[GoGently]

This is kinda interesting to me as I have a chance of aquiring a Honda insight MK1  3 cylinder hybrid which has an alloy body. Should I buy?

[spartacus]

Yes!

[Yoss]

Duralac and Monel rivets

My Routemaster has Monel rivets at least on the exterior though some people don't know this when replacing panels. Though they may have skimped on the interior (non load bearing) ceiling panels which results in any paint you might put on falling off again. Ive just left it now just rubbing off the loose stuff. There's now no paint within half an inch of the rivets, except the original LT primer, that must be good stuff.