Galvanic Corrosion - Wishbone Bush Sleeves

[Hypersonic]

Recently had an issue with removing a 2019 ND lower front wishbone forward bolt from it’s inner bush sleeve.The bolt was seized solid in the bore of the bush sleeve.
The bush sleeve is an aluminium alloy and the bolt appears to be zinc coated. Dissimilar metals, a recipe for galvanic corrosion.
Not wanting to go through this nightmare again, I suggest the following : 1. Do not use copper based greases, as they promote galvanic corrosion by way of their conductive and dissimilar nature. 2. Do use ceramic based greases, as they do not promote galvanic corrosion. Or if connecting a alloy bush sleeve (aka OEM upper & lower wishbone arm bushes), via a galvanised steel bolt, then Aluminium base anti seize compounds are also acceptable.

Happy to hear of any other methods of avoiding seized bolts.

[MickAP]

I’ve been using a product called Bostik ‘never seez’ on any bolts or mating surfaces that may require disassembly later.
Recently front hub replacement, they were rusted on solid, alloy wheel to hub mating surface and of course any nuts bolts that are prone to possible seizing under the car.

I was fortunate enough to be provided with a small tub by my neighbour who’s an engineer, it’s expensive to buy.

[CBRDEANO]

Have always used aluminium anti seize paste.

[Hypersonic]

Have researched a little more : I present The “Electronegativity Chart” .

The further the elements are away from each other in this chart, the more reactive they will be when joined together. Our aim is not to turn our bolted joints into small batteries by choosing metals that are as close as possible to each relative to the Pauling scale (as shown in the above chart).

So using Aluminium anti seize compound would be less reactive when used with a zinc coated steel bolt and a aluminium alloy bush sleeve. Nickle based compounds however, would be more reactive and produce a higher Galvani Potential (Galvani potential - Wikipedia).

So I like the Aluminium, in preference to the Nickle base compound, but still like my ceramic based compound the best ATM. As usual, it’s all a question of “Nobility”.

[Hypersonic]

Have now bought some Aluminium anti seize compound, so will put Aluminium on one side & Ceramic on the other.

Will report back in 10 years time

[Dean_S550]

Don’t know if it’s still available but there used to be a great product called Duralac for preventing corrosion on dissimilar metals to be put together, such as bolt threads and the like.

[Hypersonic]

Hi Dean, thanks for the reply. I checked out Duralac here : Duralac Anti Corrosive Jointing Compound 115ml - mbfg.co.uk.

It was looking good until I got to the application section : “It will harden somewhat if a thin film is left exposed to the atmosphere for a long period and this will prevent the making of a close joint.”

I’m sure it works great on marine applications (and which should be good enough for cars), but that word “Harden” has put me off.

If we can find out what grease they used on the James Webb Space Telescope or Elon’s Tesla Roadster, then maybe just maybe, it will be good enough for an MX5.

Cheers

[Dean_S550]

Fair enough. I think any hardening of the grease will be trivial in comparison to trying to free metal parts that have seized together. Even if the grease did harden to an extent as long as it coats one or both metals then the joint should be good

[CBRDEANO]

I use and have used for years Loctite LB8150
Never had any issue with it regardless of where it has been used.

I was put on to it by the guys who assemble the Thermoking Trailer units.
The refrigeration pack on the front of a trailer unit will typically not be removed for 5+ years and they are outside in all weather conditions.

[Mazda_mender]

Never had any issues using the "devils"copper grease for the right applications where needed, as the same with any other lubes.
M-m

[Hypersonic]

Thought I’d include some recent corrosion examples and perhaps provide something to ponder ref. preventative maintenance.

The top one is a rear lower shock bolt and the bottom one is a rear suspension cam bolt.

This is the lower shock knuckle bush.
I don’t have an expensive high torque impact wrench (which may have speeded things up), so I set to work with a mapp gas blow torch (careful not to over heat the rubber bush material), a 600mm breaker bar, a lump hammer and lots of WD40 (sounds incredibly like a line from “Pulp Fiction”).
The lower shock has a captive nut, so only the bolt head needs to be turned. The technique was to heat up the bolt and then tighten and untighten the bolt repeatedly. 4 hours later, I had freed up and removed 4 bolts. I then cleaned out the bush bores with a plumbers 15mm wire brush and coated everything in aluminium Sealey anti seize compound.

As with most cars, they are built “dry” at the point of manufacture, so disassembling vulnerable fixings and adding the appropriate lubricant, is always a good long term ownership plan (unless you live in California).

The above bolts in the rear suspension were 10mm diameter (17mm socket), but the front lower wishbone arms are 12mm diameter (19mm socket). These 12mm bolts corroded into the lower wishbone bushes were a whole new ball game.

Luckily, I needed to change my front subframe. The LHS had all new suspension components, on the RHS however, I needed to recover the RH lower wishbone. Once cut out of the subframe (see pic), I handed it over to a friend with a workshop who initially tried to press it out using a hydraulic press. After 13 tonnes and turning his head away, he decided to drill out the bolt. This proved successful, but he said it was difficult to drill and keep the rubber cool.

So, something to ponder if you live in a country that uses salt on it’s roads.

PS. “Zed’s Dead”