Is it possible to get these washers in some other material?

[Mawrick 0]

Anyone know if it's possible to get these washers in a material that doesn't "eat" the aluminium it's supposed to be securing.

 

Or any tips on anything one can treat them with to make them not react?

 

 

The washers I'm talking about is these ones:

 

 

(holding the heat-shield etc)

[davidwort 0]

they seem to be a very springy steel and galvanised, they're more of a nut than a washer :) where about's have you had trouble with them because most of mine and a lot I see on old golfs etc in scrap yards are in pretty good nick, as they are exhaust heat shields they support, are yours in a very high heat area? you could paint them in high temp paint or hammerite or something before fitting new ones.

[Mawrick 0]

Can't remember exactly where the ones that had "eaten" thru the aluminium is, but it was on the head shield running on the underside of the car, above the exhaust pipe.

 

But you are right it's not like it's all of them, was just wondering if anyone else has this "problem" and maybe if they had any ideas if it was alternatives to these ones...:)

[aide 0]

could be a result of bimetallic corrossion where a current passing through the interface causes the less noble metal to erode, I've come accross it in metal cladding systems and the only way to overcome is to space connections with a rubber washer :D

 

worth trying what david says, could cut down the interface some

[davidwort 0]

bimetallic corrossion where a current passing through the interface causes the less noble metal to erode

 

:lol: I have no idea what you are on about but it sounds great or nasty!

 

do we have a metalurgist (spelling?) on the forum?

 

just out of interest, I take it heat would be a major factor in this, as clamped on downpipe shields and exhaust manifold heat deflectors (for warm air pickup) seem to corrode very fast too.

[iceviolet 0]

I made some of these out of a bean tin lid and some tin snips. Does the job but not the prettiest pieces. cheap though! :D :D

[aide 0]

:lol: I have no idea what you are on about but it sounds great or nasty!

 

do we have a metalurgist (spelling?) on the forum?

 

just out of interest, I take it heat would be a major factor in this, as clamped on downpipe shields and exhaust manifold heat deflectors (for warm air pickup) seem to corrode very fast too.

 

i'm not sure what i'm on about either :D introducing heat into a metal definitely creates a low voltage charge but a charge all the same, what definitely makes a difference is if the connection is wet as that makes conduction/ erosion even quicker - something to do with creating an electrolyte liquid :scratch:

[davidwort 0]

Come to think of it 2 different metals, like a steel bolt in an alloy component can sieze in quite nicely, add lots of heat and plenty of splashing with salt water and I guess it's hardly surprising it doesn't take long to make a mess.

After spending most of last saturday having to drill out the rear bumper mounting bolts on my car I think I might be replacing them with stainless ones.

[mikkijayne 0]

We are basically making a battery here. Two dissimilar metals - zinc & aluminium, and an electrolyte - water (salt water in the winter).

 

The joint between the aluminium and the galvanised washer produces a tiny charge as Aide said, and it transfers metal ions from one side of the 'battery' to the other. It starts off taking the zinc from the washer, as that is happier to give away ions than aluminium (hence why you put zinc anodes on aluminium outboard motors on boats so the sea water eats the zinc and not the outboard!). Once the zinc has gone the washer goes rusty and then you have steel and aluminium together and the process reverses. You then get the steel washer pinching ions from the aluminium heat shield which makes it oxidise really easily (making the white fluff), and the heat shield starts disintegrating.

 

The best solution for this is to put a non-conductive layer between the two parts (as Aide also said), or just replace them every now and then before they go rusty. The rubber washers used to hold the heater box in would probably work, although they might be a bit small. Thin plastic sheet would also work as few of these clips are in a direct heat source, apart from the couple above the rear silencer.

 

Manifolds and downpipes rust easily because the heat cycle they go through just makes formation of iron oxide that much easier.

 

/science nerd :lol:

[aide 0]

top explanation mikkijayne :salute:

 

i was only half paying attention in class :)

[Kevin Bacon 5]

Blimey, you'd have thought VW would have considered that, but obviously not, as they still use the same method to secure the heatshields to the floor :lol: Or is it engineered in weakness to force you to buy new heatshields? :D

 

Mine are corroded away around those retainer clips too, but I just used bits of bracket to 'bridge the gaps' and put the washers back on :D

 

I'm sure the 'corrosion' is probably down to abrasion aswell. Lots of under body turbulence rubbing the two surfaces together....plus water and grit, and that battery effect.....

 

Oh and the plastic nuts they use to secure various things around the engine bay and interior, they screw on OK with some plastic / rubber washers.