Undertray bolts

[Lotobear]

I keep my undertray bolts copper greased but each time I remove them I see the effects of electrolytic corrosion on the aluminium trays and was thinking - has anyone put together a stainless bolt set?

....not only would they look good but they would remove the lingering concerns over seized bolts and corroded aluminium

[C8RKH]

This may help

https://www.lotustalk.com/threads/heres-whats-in-a-full-stainless-steel-hardware-kit.409417/

[#84]

I did the opposite, went for Aluminum screws with big rounded head for minimized drag and weight 😱

Sorry, not in English, but you get the principle: https://www.carbix.se/product.html/aluminiumskruv-kullrig

[au-yt]

Forget what google will tell you don’t put stainless and aluminium together especially in any moisture type environment dissimilar metal corrosion is the result. 304 stainless is especially bad.
I’ve seen stainless turn to a black almost grease Type substance when bolted to aluminium in a drain water sump and it’s also a no no around swimming pools. 
If you do use stainless bolts you need to use a nickel based anti seize. 

[C8RKH]

You can use a plastic paper thin washer between the stainless and aluminium can you not to avoid the physical contact point.

[Bibs]

https://www.mbfg.co.uk/duralac.html

[Nelly]

I am in the process of removing my undertray so I can remove the 3rd cat and fit a straight through pipe.

I think the rust even surpasses what I have seen on my Esprit.  Shit the bed what a job to get it off, I am having to cut them with my dremel as the bolts are solid.  With them being hex head as well doesn't help (although one did bite enough to actually snap one of the captive nuts off of the plate it was welded onto) - very helpful.  Wheel off to get to that!

 

[DarrylV8]

Always used Vaseline when using two dissimilar metals, and copper grease on the back of brake pads.

[Bibs]

28 minutes ago, DarrylV8 said:

Always used Vaseline when using two dissimilar metals

Duralac is the correct product to prevent galvanic corrosion. 

https://www.mbfg.co.uk/duralac.html

I'd imagine vaseline would get washed away by water very quickly after application.

[EGTE]

Have just ordered and put Duralac on mine, thanks for the tip, Bibs.

[Julian73]

On 07/09/2020 at 08:23, Lotobear said:

I keep my undertray bolts copper greased but each time I remove them I see the effects of electrolytic corrosion on the aluminium trays and was thinking - has anyone put together a stainless bolt set?

....not only would they look good but they would remove the lingering concerns over seized bolts and corroded aluminium

I went with SS button hex-head machine screws and use USS Tef-Gel PTFF anti corrosion paste.  Tef-Gel is also good for insulating CF products from SS screws and aluminum.

 

https://www.tefgel.com/contain.php?param=tefgel_infor

[Nelly]

OK, after five Sundays I have finally got the under tray off.  I had to butcher eight of the bolts to get them off so ordered some replacements.  I went for black stainless steel bolts from Carbolts:

https://www.carbolts.co.uk/collections/bolts/products/black-stainless-steel-button-flange?variant=8135052329078

But having read the above, not sure what I should be doing.  Am I better off using the stainless bolts I have just got using one of the products mentioned, or with factory steel bolts with some copper grease?

To add insult to injury, I was doing this to put a decat pipe on the car but having got the diffsuer off found it had already been done.  Not sure what I was most upset about, all that wasted time or the fact the sound of the car won't be improving.

 

 

 

[Julian73]

Stray away from copper grease, this will not prevent corrosion infant it will an electronic path.  Better to use a product such as USS Ultra Tef-Gel

 

 

[jerzybondov]

On 27/09/2020 at 21:25, Nelly said:

To add insult to injury, I was doing this to put a decat pipe on the car but having got the diffsuer off found it had already been done.  Not sure what I was most upset about, all that wasted time or the fact the sound of the car won't be improving.

 

 

 

Does this mean you've got a decat pipe going spare?  Interested if so!

[Nelly]

@jerzybondov - Yes I do, it was going to go up on the classifieds at the weekend.  Will drop you a PM

[Tris...]

On 29/09/2020 at 17:20, Julian73 said:

Stray away from copper grease, this will not prevent corrosion infant it will an electronic path.  Better to use a product such as USS Ultra Tef-Gel

 

 

Great stuff Tef-Gel, use it all the time on high tech racing boats especially between carbon and aluminium. 
 

Sticky as hell so don’t get it on your clothes. 

[Spinney]

Out of interest, I fitted some of these anodised aluminium screws in place of the standard ones on the under tray of both my Elise and Exige. Never had a corrosion problem with them after that. 
https://www.ebay.co.uk/itm/M5-Aluminium-Socket-Cap-Screws-Allen-Key-Bolts-Hex-Head-Anodised-Unanodised-/282771602905

If you want to be a complete tart (ok I’ll hold my hand up😁) you can choose a colour to almost match the cars bodywork.