Better than powder coating for subframe?

[CoolHands]

Planning ahead I will want to get my front subframe blasted and protected. I’ve never liked powder costing I see it as a bodge that hides creeping rust - see TVR chassis for examples

Is POR15 two part epoxy that sets hard any good? Or what. I’ve also read about ‘zinc phosphate primed’ and then painted. Is that commonly available?

Edited by CoolHands on Thursday 17th August 20:28

[Darumvej]

Zinc metallizing

[colin_p]

Darumvej said:

Zinc metallizing

You mean galvanising.

To accompany that, you'd want it acid dipped then galvanised.

For reference, POR15 is very good stuff but won't be as good as galvanising.

[Darumvej]

colin_p said:

Darumvej said:

Zinc metallizing

You mean galvanising.

To accompany that, you'd want it acid dipped then galvanised.

For reference, POR15 is very good stuff but won't be as good as galvanising.

No. Zinc metallizing is correct but expensive.

[colin_p]

Darumvej said:

No. Zinc metallizing is correct but expensive.

Would you mind explaining the process vs galvanising, I'm genuinely interested to learn.

[tr7v8]

My Westfield chassis had been powder coated I assume at the factory. A few years later when rebuilding it was awful. The PC came off in sheets with your hands. I ended up with a very heavy tin of cold galvanising Zinc & brushed that on the freshly prepped metal. Then Valspar type black gloss. You will chip it & the black gloss is A. dead easy to touch in & B. because its easy you will do it.

[colin_p]

colin_p said:

Darumvej said:

No. Zinc metallizing is correct but expensive.

Would you mind explaining the process vs galvanising, I'm genuinely interested to learn.

I've been having a look online.

I'd say that for a subframe with otherwise inaccessible nooks and cranies, that hot dip galvanising would be best.

[TwinKam]

Powdercoating has got itself a bad name but it's actually down to the prep rather than the product.
But a layer of zinc under a 'painted' coat is a great idea as, if the paint coating is damaged, the zinc still protects the steel underneath.
Galvanising involves immersing the whole structure in a bath of hot zinc solution but, due to the heat involved, every sealed void eg tube needs to have a vent hole drilled into it to allow gas to escape. This doubtless is a great treatment, it certainly works for Armco, but there is a risk of warping on some structures.
Hot zinc spraying is a rather less immersive (sorry) process in which zinc wire is vaporized and transferred onto the structure with a flame from a special torch, but the heat involved is far less than galvanising and it requires no vent provision, but clearly the insides of sealed voids eg tubes remain uncoated.
The process of choice for most TVR restorations is this hot zinc transfer process followed by a coating of marine epoxy mastic eg 'Jotun Jotamastic', usually sprayed on.

Edited by TwinKam on Thursday 17th August 22:08

[donkmeister]

Just to add a third zinc process into the mix... Is electroplating an option? Whilst it's inferior to hot-dipping it should be cheaper, with no risk of warping and as it's not sprayed it would give better coverage to the internal nooks and crannies than metallising.

ETA I just looked it up and electroplating is effectively line-of-sight, so it won't properly plate any areas where the anode is obscured (e.g. inside tubes).

Edited by donkmeister on Friday 18th August 01:35

[Boosted LS1]

Could you tuftride it? I've had steering parts done and hope it'll last.

[CoolHands]

Yes that was an interesting read about Salt Bath Nitrocarburise (Tufftride is apparently a trade name of the progress). It looks to me that it’s more aimed at solid items like camshafts etc ie not great for lots of internal nooks and crannies like a subframe.

https://www.wallworkht.co.uk/content/salt_bath_nit...

Galvasing isn’t great in terms of blocking up holes and bolt holes - it is quite thick and I think on balance it would annoy me.

I think overall I might see about getting it shot blasted then simply painted by POR15 or similar, (or maybe that Zinc metallizing) and perhaps spray some wax stuff internally through the holes.

Edited by CoolHands on Friday 18th August 12:25

Edited by CoolHands on Friday 18th August 12:29

[droopsnoot]

If you're painting with POR-15, have a look at their surface preparation product. I've seen times where the dried product will simply peel off a smooth surface if the prep isn't used - it'll stick to rough parts without it. I didn't use it, and probably should have done. Also beware of trying to poke a hole through the skin that will form on top of a part-used paint can - I found it quite difficult to remove from skin when I foolishly did that.

I've never liked powder coating on suspension parts - if it does get damaged it's impossible to repair and water can sit between the coating and the metal and cause more trouble through not being able to drain away or dry in the air. You've either got to mask off where any interference fit bushes go (and have an edge that can pull back) or try to press bushes in and damage the powder coat in the hole. I had one done, it looked really nice, but I sold the car soon after and the new owner reports that it didn't last long.