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Galvanising Preparation and Tips


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Hi,

I'll just take this opportunity to say hello to everyone on the group. Also thanks for all the help I've have had so far reading through all your posts. I threw myself in the deep end and bought a 110 1996 300tdi. I'm currently rebuilding it onto a galvanised chassis and have now decided coming onto the bulkhead to repair and galvanise also.

So I've finally managed to get my bulkhead stripped and I'm dropping it off to get blasted tomorrow. What I would like to know is after I've to the necessary welding repairs to the footwells, vents, and pillars what prep to do to the bulkead before getting dipped?

I've seen removing the vents, but what do I do with all the small self tapping holes and the bolt holes to never see them again and my life becoming a game of hide and seek. Haha!

Also is it possible to put an old bolt in the captive nuts to stop ruining the threads? I can only see this being the way but will defeat the object of galvanising?

Thanks in advance for your help.

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I've had the same thoughts as it's on my list, there's a 2004 bulkhead sitting in my workshop patiently awaiting the same treatment.

Biggest problems I can foresee are the vent hinge holes, these are small and really close to the bulkhead face so difficult to get a drill to. Perhaps one of those right-angled attachments or even a long bit in a dremel is the answer here?

Riv-nuts are also prevalent across the unit, these will need careful drilling out/tapping to avoid spinning them in their holes. The alternative is to remove them, but this is easier said than done without leaving the barrel floating around inside the cavity. Though I guess the zinc should 'glue' it in place and avoid rattles - it's a less than ideal solution.

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I can confirm the vent hinges hole were a tad of a hassle to say the least to get clear.

Also the bolt holding the angle iron across the bottm lets, one came out ok, the other sheared off, but drifted out ok.

All other holes had to be re-drilled to allow the bolts to pass though or be re-tapped

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Vent flap hinge holes were the worst bit on mine.

I used a drill bit with hex drive, and a flexible 1/4 drive extension in a cordless drill. Took ages as you couldnt apply much force due to the flexible thing and the drill bits i'd bought were hopeless nasty things off ebay made from monkey metal.

Everything else drilled and tapped out just fine. A mate suggested leaving bolts in all the holes, and nuts on the various studs, but i didnt bother in the end.

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Ok so basically you just have to persevere with the vent holes. Where did people drill air escape holes in the cavity? I have been looking and I was thinking the engine bay side of the cavity at the bottom and maybe just below the window in the cab side?

Any other areas? What about the posts?

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Had mine done a few months ago. As others have said you can't use any sealant in the holes as the heat will destroy it. Even small holes are still visible afterwards as a dimple so can be drilled out. Rivnut holes just need to be drilled out enough to get a tap in and then retap.

Do all repairs prior to galvanising. The galv firm will insist on it then being shot blasted. Either sort this out yourself, or they may have a local shotblasters they deal with.

They only additional holes I drilled were inside on the bottom sloping sections of the footwells. This section is double skinned (or was on my early Td5 version) and it wanted the insides galved. A drilled a series of 10mm holes from the inside in the double skinned bit. I shall plug these with rubber grommets.

I drilled out the spot welds to remove the vent flyscreens - I will use the series alloy types refitted with pop rivets. I drilled holes in the bulkhead for these before getting it galvanised.

I fitted a square section of tube as bracing between the bulkhead/chassis bolt holes. I had to angle grind the nuts off after galvanising. Turning the bolt heads then got them out with an aid of a hammer. This reinforces what other say- don't put bolts in the tapped holes.

There was very slight rippling of the section that will be hidden by the dash above where the fuse box is. Apart from that no distortion. Finish was fairly flat - especially on the visible sections above the bonnet shut line - certainly good enough to paint straight over after suitable surface prep for paint.

One surprising thing was the weight after galvanising. Prior to it being done, it was a an easy 1 man lift - if a bit of a hazard to the shins if not careful. After galvanising I could only just lift it. The invoice says 41kg, but not the weight before it was done.

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Take the rivnuts out while the bulkhead's in bits, then fit new after galvanizing

How does one best accomplish this?

Taking the flange off is easy enough, but how do you get the barrel out through the hole that it is larger than? I'm not sure all the cavities are open in the right places to be able to rattle them out onto the floor, or are they?

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How does one best accomplish this?

Taking the flange off is easy enough, but how do you get the barrel out through the hole that it is larger than? I'm not sure all the cavities are open in the right places to be able to rattle them out onto the floor, or are they?

If the bulkhead is in bits being repaired, most areas are going to be exposed so a good rattling should see them out

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Did mine 3-years ago.

Take plenty of photos beforehand and make some drawings showing EVERY hole and its approx. measurement from fixed points, some of the smaller holes can be totally invisible after dipping.

Clean off corrosion etc but the final clean is done by the galvanisers themselves with the acid-dip.

I drilled several holes in the box-sections, that way there was always a hole uppermost regardless of what angle it was suspended and when refitted to the vehicle none are visible.

DON'T try to block any holes as the zinc has to flow everywhere and the heat is very high, any sealed sections will expand and split open ruining the bulkhead (that is if the galvanisers haven't identified them first and drilled their own holes, usually exactly where you DON'T want them!).

I braced mine across the bottom with a section of 50mm box-steel, no problems with heat twisting the structure.

I removed the vent mesh and then bonded it back into place afterwards, seen several where the mesh was left in place and they effectively have no vents anymore. The vent hinges were the worst problem, very difficult (impossible) to get a drill in to clean them out but after ages of faffing around I used a long length of threaded rod (M4 if I recall correctly) and found that I could wind it in and clear the holes with ease as the rod stuck out past the pillars and could easily be twisted.

Wound a series of nuts onto every stud (all M6 if I recall correctly), no problems with any of them shearing off. The problem is if you only fit one or two nuts and don't tighten them correctly, the zinc flows along the threads causing problems whereas if the thread is completely covered and the nuts locked together the zinc can't get past.

Likewise the captive nuts, wound bolts into every one and didn't have a single problem with the bolt shearing off. I think the trick is not to wind the bolt in too far, make sure it is flush with the end of the captive-nut and then stop (use a lock-nut on the exposed side if you like to stop it moving).

To affirm what I said about captive-nuts being left in place, I recently had my Mantec steering-guard bracket galvanised and while I was at it I decided to fit captive-nuts instead of the old nut/bolt arrangement. I fitted captive-nuts, screwed in some bolts and then had it cleaned / dipped. Came back and every bolt came out without problems.

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Right I've started cutting away parts of the badly corroded vents and have seen the damage in the cavity. Being nosey of course.

My original plan was to get it blasted then cut away the damage and then welded. Now looking at this I am now considering cutting away the damage pretty much as close as I can maybe leaving a little extra to tinker with before welding. While all the cavity is exposed getting it blasted and then welding it up then getting it galvanised.

Does anyone think this is over kill or will the acid bath before dipping clean the cavity sufficiently?

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Right I've started cutting away parts of the badly corroded vents and have seen the damage in the cavity. Being nosey of course.

My original plan was to get it blasted then cut away the damage and then welded. Now looking at this I am now considering cutting away the damage pretty much as close as I can maybe leaving a little extra to tinker with before welding. While all the cavity is exposed getting it blasted and then welding it up then getting it galvanised.

Does anyone think this is over kill or will the acid bath before dipping clean the cavity sufficiently?

The acid bath will remove light surface rust, but not heavy rust. The latter invariably forms layers, so if you have that in the cavities is probably best to get it removed by blasting then weld in new metal. If stored/worked on in a dry environment any light surface rust that forms again inside should be removed by the acid bath.

LR didn't "actively paint" inside of cavities - certainly not in the new genuine parts TD5 version I'm using for my rebuild. Its more a case of paint wafting into the cavities such as the door pillars as the spray gun goes past.

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