Technical Rear Beam Corrosion

[jrkitching]

There's been a lot of discussion in the Panda section recently about excessively corroded rear beams; once the cars are about 10 years old, the beams commonly rust through to the point where they either fail the MOT, or collapse in service. See this thread for a picture of what can happen.

Now I don't want to sound alarmist, but the 500 uses an almost identical beam (the construction is the same; it's just a couple of inches wider), and it's reasonable to suppose these will suffer from the same corrosion issues as they get older. The first cars are eight years old now, and sadly I don't think it'll be long before we see the first 500 rear beam corrosion failure.

Anyone intending to keep a 500 long term might want to think about applying some appropriate corrosion protection now, whilst the beam can still be easily salvaged.

Also, anyone purchasing a 500 >5yrs old should look carefully at the rear beam (it's easily visible if you bend down and look under the car) as part of their pre-purchase inspection.

Panda owners are struggling because new beams are >£700 and most of the secondhand ones are beyond salvaging; any in decent condition sell for £300+. 500 owners are in a better position because decent later 500 rear beams can be had from breakers for much less money; an additional bonus for pre-2010 500's is these, if bought with springs and dampers, will also give you the improved stiffening and suspension from the 2010 facelift. (500 beams can be bolted onto the Panda, but the 500 track is different and it throws out the rear wheel spacing).

@DaveMcT has started a useful thread with a guide to replacing the beam; follow it here.

 

[John202020]

I've already wire brushed the beam and applied Tetroseal which should also be applied to the rear of the brake drum backing plate and suspension components.
I did it when I replaced the severely corroded drums.

 

[ahmett]

There's been a lot of discussion in the Panda section recently about excessively corroded rear beams; once the cars are about 10 years old, the beams commonly rust through to the point where they either fail the MOT, or collapse in service. See this thread for a picture of what can happen.

Now I don't want to sound alarmist, but the 500 uses an almost identical beam (the construction is the same; it's just a couple of inches wider), and it's reasonable to suppose these will suffer from the same corrosion issues as they get older. The first cars are eight years old now, and sadly I don't think it'll be long before we see the first 500 rear beam corrosion failure.

Anyone intending to keep a 500 long term might want to think about applying some appropriate corrosion protection now, whilst the beam can still be easily salvaged.

Also, anyone purchasing a 500 >5yrs old should look carefully at the rear beam (it's easily visible if you bend down and look under the car) as part of their pre-purchase inspection.

Panda owners are struggling because new beams are >£700 and most of the secondhand ones are beyond salvaging; any in decent condition sell for £300+. 500 owners are in a better position because decent later 500 rear beams can be had from breakers for much less money; an additional bonus for pre-2010 500's is these, if bought with springs and dampers, will also give you the improved stiffening and suspension from the 2010 facelift. (500 beams can be bolted onto the Panda, but the 500 track is different and it throws out the rear wheel spacing).

@DaveMcT has started a useful thread with a guide to replacing the beam; follow it here.

Mine looks ok, I think because in Greece it rains slightly less than in the UK. I really believe those Fiats are not made for UK climates!

 

[jrkitching]

Mine looks ok, I think because in Greece it rains slightly less than in the UK. I really believe those Fiats are not made for UK climates!

You'll be fine in Greece.

It's folks who live in places where they regularly salt the roads in winter that should be concerned.

 

[Baglady1990]

ok... so now the front undercarriage is sorted & me being me I'm focused on the rear
im taking on my almost 10 yr old beam..... considering the state of the car when I got her... the rear beam is in surprisingly decent condition....


BUT....last winter I decided to seal with waxoyl thinking that was best :idea:
so now so I examine I have to try remove this.... I have found out that white spirit will remove it but wanted to ask is this safe to use under the car?
there are already areas that have started to rust through the coating that I applied so im eager to get on and resolve.... luckily I have a toasty garage

if I do manage to remove this stuff what should I use instead? hammerite paint?
I really don't want to be in a position of having to replace....as the hub and stub removal scares me to death...

 

[chris3234]

White spirit should take I off fine just wear gloves and eye protection
I'd you have access to a compressor it try stone chip or truck bed liner paint

 

[jrkitching]

ok... so now the front undercarriage is sorted & me being me I'm focused on the rear
im taking on my almost 10 yr old beam..... considering the state of the car when I got her... the rear beam is in surprisingly decent condition....


BUT....last winter I decided to seal with waxoyl thinking that was best :idea:
so now so I examine I have to try remove this.... I have found out that white spirit will remove it but wanted to ask is this safe to use under the car?
there are already areas that have started to rust through the coating that I applied so im eager to get on and resolve.... luckily I have a toasty garage

if I do manage to remove this stuff what should I use instead? hammerite paint?
I really don't want to be in a position of having to replace....as the hub and stub removal scares me to death...

Post some pictures of your beam; it'll help us work out what's best for you.

If the beam is sound, your objective should be to keep it that way; you want to rust proof it, not achieve a showroom finish - nobody but yourself and your MOT tester is going to be looking at it.

Actually, good old fashioned waxoyl isn't that bad a choice; you can apply it directly onto rust and it will definitely slow down its progress considerably; you just may need to apply some more over the areas where it's still showing some rust. The spray cans are relatively expensive, but handy for this application and one can will do the whole beam. Just spray it onto the beam and springs and rub it in whilst wearing a decent pair of nitrile gloves (it'll eat through most other types). You might have to repeat this every year, but it'll only take you half an hour and realistically will likely protect the beam sufficiently to last the remainder of the useful life; no dismantling required. This is what I do on my Panda.

Dinitrol make a similar, though more costly, product which some folks (myself included), think is superior, but waxoyl will be good enough and you won't have any compatibility issues with what's already there.

Hammerite paint is basically rubbish and will quickly start to peel. I wouldn't even use it on a metal garden gate.

Actually, I'd forget about any kind of paint unless you're going send the beam away to be professionally derusted, degreased and chemically prepared for painting; you'll never be able to get it to adhere properly otherwise. Water & salt will get between the paint and metal and you'll be even worse off than if you did nothing. Some folks have even had the beam sandblasted, derusted in an acid bath, washed, passivated and galvanised. To get any kind of durable paint finish, you'll also need to use professional grade etch primer & a two pack paint system, all of which needs a full fat paint shop with proper forced air respirators - it's not something you do at home in a garage.

Even the best paint finish isn't very effective at preventing corrosion in a damp, salty environment. For that purpose, you want a waxy, self healing, non-setting coating, which is exactly what waxoyl/dinitrol is designed to give you.

Another option is to use mineral grease; just smear it all over the rusty bits using any reasonable method you can think of, avoiding getting any onto any rubber parts. You can use almost any kind of grease, but something like this would be ideal.

 

[Baglady1990]

As it happens I bought more waxoyl so not a bad thing and the spray not the tar pics below of beam
I have new bump stops on the way (mine are perished)

 

[John202020]

Compared to ours at only a year older, yours looks in far better Nick

 

[Baglady1990]

Compared to ours at only a year older, yours looks in far better Nick

Yeah I know but god only knows how!! Most of the other bits have been well past their sell by lol

 

[jrkitching]

That all looks absolutely fine - one of the least corroded beams I've seen recently, and the springs look like new.

Just to clarify what I'd posted earlier; you need the original, clear waxoyl; not the black underbody seal with added waxoyl. Also rub some all over the spring coils, and give the inside of the spring pans (where the springs seat) a generous spray.

Keeping the end faces of the springs greased, where they contact the spring pans, also helps to prevent squeaky suspension. Just make sure you don't block any drain holes.

 

[jrkitching]

Compared to ours at only a year older

That's more typical of a 10yr old Fiat beam.

These things left the factory with a coat of paint, which shows just how ineffective paint is in preventing corrosion in these sort of applications. IMO these beams should have been galvanised; it wouldn't have added much to the cost of the car.

This issue will likely write off a lot of 500's in years to come; it's writing off Pandas now.

 

[Baglady1990]

That all looks absolutely fine - one of the least corroded beams I've seen recently, and the springs look like new.

Just to clarify what I'd posted earlier; you need the original, clear waxoyl; not the black underbody seal with added waxoyl. Also rub some all over the spring coils, and give the inside of the spring pans (where the springs seat) a generous spray.

Keeping the end faces of the springs greased, where they contact the spring pans, also helps to prevent squeaky suspension. Just make sure you don't block any drain holes.

Phew!! Thanks so much! Yes will order some clear this evening as always thank you for the advice it’s much appreciated

 

[TurboToppolino]

When i worked in a volvo bodyshop about 25 years ago they had the volvo branded wax in amber and black. It was brilliant stuff ( probably not very environmentally friendly! ). I don’t know who made it for them ?.

 

[Gina500]

That rear axle looks nearly new, mine at 2 years is not much different. If you keep up the wax-oiling it will most certainly last forever.

It reminds me to do something to my axle, though. I only treated the spring pans last winter, but that seems not to be enough

 

[chris3234]

That's been treated with stone chip type paint at some point in its life judging by the finish
Which would explain the good condition of it just get some more of the edge's where you can see the rusty patch's

 

[Baglady1990]

Got a lot done over the last couple of afternoons! Still more to do though as always
As for the chassis rails do they need doing inside? I see rubber bungs under there or do I leave alone? (Reading back of waxoyl can has scared me) ? wheel arches off tomorrow and I’ll give that a good clean n spray same with rears as I didn’t realise you needed to do that too! Any other areas anyone can suggest?

 

[jrkitching]

Reading back of waxoyl can has scared me

Just remember they're trying to sell you more of the product .

 

[Baglady1990]

Just remember they're trying to sell you more of the product .

Hahaha indeed I’m such a consumer ?