172 replies to this topic

[fezzasus]

I get what you mean with it's not as accessible but surely it would be better to have a spacer pieced corroding away than the chassis legs?...

 

Completely agree, however the rate of corrosion will be much greater because there isn't any passivisation, which is why the original spacer is zinc coated steel. A bi-metallic plate, one side zinc passivated steel and the other anodised aluminium may work.

[Mopeytitan]

I get what you mean with it's not as accessible but surely it would be better to have a spacer pieced corroding away than the chassis legs?...

  Completely agree, however the rate of corrosion will be much greater because there isn't any passivisation, which is why the original spacer is zinc coated steel. A bi-metallic plate, one side zinc passivated steel and the other anodised aluminium may work.

Ah yes course it will! original lotus parts will be best then!

[Aerodynamic]

Can I mount my rear support pillars between rollcage and subframe when the car is on jacks, or when its on its wheels? Br, Per

[fezzasus]

Can I mount my rear support pillars between rollcage and subframe when the car is on jacks, or when its on its wheels? Br, Per

 

wheels

[nicollow]

Does anyone have any experience of a good place to go for surface retreatment or re-galvanising of the sub-frame? Im hoping to get round to this over winter and would prefer just a Google stab in the dark. Cheers

[ukcat]

Does anyone have any experience of a good place to go for surface retreatment or re-galvanising of the sub-frame? Im hoping to get round to this over winter and would prefer just a Google stab in the dark. Cheers

 

Hi Just be careful here !! -  Just be aware that when items are galvanized there is often some fettling work required afterwards on areas like threads or bolt holes etc where the build up of zinc needs to be removed - Generally this can be done by re-tapping,drilling, grinding etc.

 Obviously when you clean out a threaded hole (normally with a tap) you need to try and run the tap through the original thread and if you are not careful it can be quite easy to cross thread or cut a new thread !! - I Have experience with tapping clogged threads and generally with care and sometimes using a low temp blow torch to soften the zinc it can be achieved fairly easily.

My concern here is with the upper mounting threads !!- I know some of the lotus guys have successfully re-galvanized however as far as i know the upper mounting bolt on the Elise (some of the models) uses a normal nut and not a recessed captive nut like ours - The issue with this top mounting hole is that it would be difficult to get the tap to accurately engage with the original thread. 

I am not sure if there is a way around this i.e can the thread be protected during re-coating or if there is a way to clear it out successfully obviously it was done when the frame was produced 

Anyway just something to think about 

Cheers 

Tony

[Nev]

Importantly, when you re-cut the threads (ie deliberately removing the zinc from them) you will likely end up with subframe to bolt contact which partly/probably negates the whole point of galvanising it in the first place.

[sford]

Back on this topic, this corrosion occurs regardless of exposure to water and mileage? Is age the key factor? 

[vocky]

my 2003 vx had zero chassis corrosion, even the shims only had a tiny amount of surface rust, so it's not age related

 

But it has been garaged it's entire life

[fezzasus]

Back on this topic, this corrosion occurs regardless of exposure to water and mileage? Is age the key factor? 

 

Water and salt are required for galvanic corrosion

[FLD]

I wonder how long it will be before someone tries to replace the corroded part. It's crossed my mind to have a go on a scrap chassis. Obviously alignment will be tricky! I wondered if the rivets in the side help with that. A blow torch to melt the adhesive and rebonding would do it. You'd just need a brave pill to drive it afterwards.

[vocky]

you could fill in the corrosion with a suitable liquid metal, but in my experience it is the steel subframe which takes the brunt of the damage* and thats what needs repairing the most

 

* the subframe gets deformed by the corrosion

[tommobot]

I haven't had time to have a good look but presume this can be reused?

There's a slight intent from the corrosion growth.

FYI, 85K and left outside most of its life.

What's the general consensus on refinishing?

I'm thinking powdercoating..

[fezzasus]

don't powdercoat. As soon as you clamp the surfaces together the powercoating will crack and expose bare substrate. Use high zinc paint if you're going to refinish and overcoat with a two part epoxy coating that will chemically bond to the substrate

[ditonics]

Personally I had mine blasted and then I cold galvanised them. On reassembly I coated both sides with duralac.

[tommobot]

don't powdercoat. As soon as you clamp the surfaces together the powercoating will crack and expose bare substrate. Use high zinc paint if you're going to refinish and overcoat with a two part epoxy coating that will chemically bond to the substrate

 

The zinc paint i'm OK with finding but do you have any suggestions for a two part expoxy spray?

 

Also, thinking about it futher if I was powdercoated I would anticipate that it have to grind back the finish a bit to fit the wishbones / dampers.

 

Isnt this going to be the same with zinc paint and a epoxy coating over? - Or am I overthinking this.. 

[fezzasus]

Powercoating does not bond to the surface, it melts to form a case around the metal. As soon as you bend the metal or crack the powdercoating you will trap moisture between the powdercoating and the surface and accelerate corrosion. Epoxy forms a chemical bond to the surface so it is less likely to crack when the metal is bent, and will protect the rest of the surface even if damaged in one area.

 

https://www.bilthamb...gs/epoxy-mastic

 

You could also apply POR15 as a paint or spray

[FLD]

As a random aside.....
would giving the joint a douse in oil once a year with the service stop this? I'm just wondering if oil is enough to stop the galvanic corrosion. Obviously it will help keep water out. Any thoughts fez?

[fezzasus]

As a random aside.....
would giving the joint a douse in oil once a year with the service stop this? I'm just wondering if oil is enough to stop the galvanic corrosion. Obviously it will help keep water out. Any thoughts fez?

 

Something like ACF50 would work. Probably best to do it before they start salting the roads, and again once they stop.

[Nev]

don't powdercoat. As soon as you clamp the surfaces together the powercoating will crack and expose bare substrate. Use high zinc paint if you're going to refinish and overcoat with a two part epoxy coating that will chemically bond to the substrate

 

Take note MBES, now you've heard it from 2 people.