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Hi all , have just started my next project a 300tdi 90 it's fully stripped down will start a thread and post some pics up of progress along the way shortly. Now its stripped the first job is the chassis its in pretty good nick needs a bit of welding in the usual places of behind the gearbox xmem and the a frame xmem , its off to the shot blasters Monday so will know more when it comes back of the full extent of the rot. I can get it galvanised at work as we have our own plant , but as its an old chassis is it worth hot dip galving it or would cold galv paint be better .

I'm asking as I've read in another thread that the galv won't stick and it will rust from inside out , then I've read an article were it said that it can be done as long as its dipped first. So whats everyone's thoughts on this ?

cheers Ian

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Yes bulkheads going to the blasters at same time then footwell repair then having that galved at work as well , it's really handy having a galv plant at work shame it's not a few years down the line as they're building a powder coating plant in the next few years . Only  parts I'm not sure about is the axle casings as they will be galved on the inside as well .

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I have been reading about coatings and was surprised to read the following on a TVR forum:

I don't care what anyone says, even the best powder coat job is utter rubbish when compared with a two part epoxy based wet paint system.

People should know powder coat does not chemically bond with the substrate, it is effectively a wrapping, once breached water will pass between it and the substrate, just one small stone chip is enough to start the process and the resulting corrosion is both inevitable and impossible to stop without media blasting the affected area and applying a new top coat.

Localised repair of breached powder coat is rarely successful in the long term because no matter how hard you try to remove the powder coat from the affected area you almost inevitably never take it back far enough, also the edges of the powder coat in your prepped are creates a zone of extreme vulnerability.

If you do have to touch up powdercoat you'll be using a brushable wet paint system anyway, in which case PoR15 works well but no matter how good the paint is, touching up breached powder coat is merely delaying the inevitable.

Nothing (& I mean nothing) offers better resistance to corrosion for mild/high carbon steel than galvanization, look at farm gates, motorway Armco & street signs, all galvanized with no top coat and lasting for years.

When it comes to top coats, nothing (& again I mean nothing) is as tough and durable as a decent two part epoxy based wet paint system, and epoxy mastic paints offer additional protection against abrasion damage (stone chips in our case) due to their incredibly flexible high solids.

Combine galvanization (even hot zinc spray) with a decent two part epoxy based wet paint system (preferably epoxy mastic) and as long as the zinc is pacified with a mordant solution and an acid etch primer is used before applying the epoxy mastic the steel beneath it will last indefinitely.

 

As I said, they are not my words but they "sound" wise to me and might help you decide.

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I'm preparing to get my existing, 26 year old chassis hot dip galvanised.  In discussions with the firm who will do it they requested that I get it sand blasted to "white metal" condition to ensure zinc adhesion.  They will acid dip it before the hot dip to remove any mild surface rust that might have formed after blasting.  It is this acid dip that is the only way to remove rust that is inside the chassis, and since most people reckon that the major corrosion is from the inside, acid treatment is essential.  I have no idea how effective this is, but from the reports above it seems to work.

If you are considering painting your HDG chassis this page gives some very useful, and important, advice.  For example, tell the galvaniser that you're going for a duplex protection system, and that your items are not to be quenched when removed from the zinc bath.

https://www.galvanizeit.org/education-and-resources/publications/category/painting-over-hdg

Hope this helps you.

Mike

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