Protecting new parts from rust

[The Mighty Quinn]

Don't hurt your head too much about it, Simon

For the subframe, get some cavity wax sprayed inside - I wire-wheeled the exterior surface too and added epoxy mastic, but I'm not sure that I should have bothered. Will be putting Dynax UB on it anyway and as long as that's looked at and repaired periodically, it should be fine.

The original subframes (without any real protection) have lasted 10+ years (and counting) - so, unless you're thinking of making the car a museum piece, don't get too bogged-down in the detail. Will any coatings applied to mild steel really keep things perfect for 10+ years? By the time we find out, the subframes will probably be further down the list of priorities!

Keep it clean and regularly looked at / repaired (Bilt Hamber and Dinitrol cavity / UB waxes seem to have a good reputation, so may be no harm in adding some of these) - I really don't think there's any "fit-and-forget" solutions to rust care.


Good luck,
Karl.

[Blink]

The problem as I see it is that the black factory paint is poor and it's prone to flaking after a few years. So the rustproofing (Bilt Hamber, Dinitrol, etc) is no longer attached to actual metal - it's attached to flaking paint.

[The Mighty Quinn]

Originally Posted by Blink

I'm putting new parts on the underside of my car and I'm looking for advice/ideas on how to protect & rustproof them before they're bolted back on.

New parts include rear subframe, trailing arms, upper & lower arms, brake backplates, discs, hubs, rollbar, etc.

The factory paint on these items isn't the best so I don't know whether to just put more paint on top of the existing paint (after keying it) and then apply wax over the top of that.

Or ...

Strip all the existing paint off (sandblast?) and repaint with primer and top coats, then apply wax on top. This is obviously a very expensive route to take.

Any suggestions?

Rear Subframe: Cavity wax inside / UB wax outside (epoxy mastic might be beneficial on the exterior, but the subframe is very exposed to debris and will always take a beating, so not sure if there's any paint/coatings that will stand up to too much in this regard - regular maintenance is key).

Trailing arms: Corrosion isn't going to be much of an issue with these - they're of very heavy-duty steel construction. Paint up and wax all around the trailing arm to body brackets though, as these seem to be the weak point. Bushes will be replaced in the trailing arms many times before corrosion becomes a problem.

Upper and lower arms: Get cavity wax products injected inside and UB outside. These are consumable items and if we get 10 years out of these before they need to be renewed, that's probably not bad.

Brake backplates: Again, I'd call these consumables - just buy a spare set or two, if you're planning on keeping the car for over 10 years (my originals lasted 15 years).

Discs/hubs: You can get pre-painted discs that will delay the corrosion process, but these too, are consumables - and would be difficult to rust-proof to any meaningful extent.

Rollbar: This will always take a beating, so whatever you apply, just check on it regularly and touch-up as required.

If your car is a daily driver, I think the above approach is reasonably practical and cost-effective.


Cheers,
Karl.

[The Mighty Quinn]

Originally Posted by Blink

The problem as I see it is that the black factory paint is poor and it's prone to flaking after a few years. So the rustproofing (Bilt Hamber, Dinitrol, etc) is no longer attached to actual metal - it's attached to flaking paint.

Yes, the factory-applied paint coatings (on our suspension parts) are terrible. Get the wire brush out and clean off any loose or flaking paint and apply some of your own primer/paint (assuming you have new parts, not yet on the car?) - then do the waxing. No coatings are going to last forever (particularly on rear suspension items), so you'll just have to maintain and touch-up as you go along.


Cheers,
Karl.

[AndyN01]

Originally Posted by Blink

Good idea if it works - have you tried it yourself?

Only on some old cast iron garden furniture.

It certainly strips off the layers.

Andy.

[Blink]

Originally Posted by The Mighty Quinn

Rear Subframe: Cavity wax inside / UB wax outside (epoxy mastic might be beneficial on the exterior, but the subframe is very exposed to debris and will always take a beating, so not sure if there's any paint/coatings that will stand up to too much in this regard - regular maintenance is key).

This is the main one I'm worried about. It's a new part but the factory finish is so poor that it's already been touched it up even before it was sold to me - the areas you can see with matt finish have all been overpainted. Other parts of it look like the factory painted over loose swarf! (You probably can't see them in this pic 'cos the website won't allow high res pics to be uploaded - they're there though).



There's no way I'm going to fit it like this. Once it's on the car, it'll be staying there for good - I'm not going to do all this work twice . So it definitely needs a proper job doing. I was really impressed by Jim's sandblasted and repainted one here (4th & 5th pics) and I want mine to have a similar job before it goes on the car. It's doubly important because the upper surface can't be reached once the frame is bolted into place.

Originally Posted by The Mighty Quinn

Trailing arms: Corrosion isn't going to be much of an issue with these - they're of very heavy-duty steel construction. Paint up and wax all around the trailing arm to body brackets though, as these seem to be the weak point. Bushes will be replaced in the trailing arms many times before corrosion becomes a problem.

I agree - the toe-in adjustment brackets are the weakest point here. I bought a brand new pair on eBay for £39.95. plus 6 new bolts to go with them from Spalding Fasteners.

Originally Posted by The Mighty Quinn

Upper and lower arms: Get cavity wax products injected inside and UB outside. These are consumable items and if we get 10 years out of these before they need to be renewed, that's probably not bad.

These are the second-worst parts to have to change on the rear end so I don't want to have to re-do them in a hurry. I think they need the same treatment as the subframe above.

Originally Posted by The Mighty Quinn

Brake backplates: Again, I'd call these consumables - just buy a spare set or two, if you're planning on keeping the car for over 10 years (my originals lasted 15 years).

Discs/hubs: You can get pre-painted discs that will delay the corrosion process, but these too, are consumables - and would be difficult to rust-proof to any meaningful extent.

Rollbar: This will always take a beating, so whatever you apply, just check on it regularly and touch-up as required.

Yes, all of these parts are so easy to change that they're not worth worrying about too much. Just a really good coating of wax on the new ones (not the discs, obviously ) and put them on the car.

Good idea to get some spare backplates btw.

Originally Posted by The Mighty Quinn

.....assuming you have new parts, not yet on the car?

Yes, absolutely everything is new (including all nuts, bolts, washers, brake hoses) - and no, I haven't put any of them on the car yet.*

* I'm still trying to sort out a new trolley jack - at least that's my excuse and I'm sticking to it.

[T16]

Factory finish is so poor I get them blasted primed and sprayed on all new parts now.

Had a new rear rollbar, stripped, primed, re-powder coated. Same with all the xenon brackets, suspension arms, the lot.

Powder coat is essential for roll bars, but the rest should be wet finish, powder coat is no good if it gets chipped.

[Blink]

Originally Posted by T16

Factory finish is so poor I get them blasted primed and sprayed on all new parts now.

Had a new rear rollbar, stripped, primed, re-powder coated. Same with all the xenon brackets, suspension arms, the lot.

Powder coat is essential for roll bars, but the rest should be wet finish, powder coat is no good if it gets chipped.

What sort of blasting did they use on yours? I've just read this and now I'm more confused than I was 10 minutes ago!

Doesn't the roll bar get chipped by stones? I can't tell with mine because all the factory paint has peeled off - it came off in curved/cylindrical lengths, like a snake shedding its skin!

[T16]

Originally Posted by Blink

What sort of blasting did they use on yours? I've just read this and now I'm more confused than I was 10 minutes ago!

Doesn't the roll bar get chipped by stones? I can't tell with mine because all the factory paint has peeled off - it came off in curved/cylindrical lengths, like a snake shedding its skin!

Uve no choice but to powdercoat it really, it rubs in the bushes and paint would just wear off. At least the hardened powder coat would last longer than paint for that specific application.

[ceedy]

Another of those controversial Subjects, a bit like tyres we all have our favourites ..

But in this case I would give any part you want to protect an good coating of " BondaPrimer" and then as many coats as you fancy of a Rubberized Sill guard type paint . and then as mentioned before what ever is your favourite cavity wax , smother the insides.

Did mine 5 years ago and still looks the same



C