Building the perfect 90

[erover82]

Curious, why can't you just blast the whole thing? I read in the last that some do that, then a process of etch, prime, paint...great update

Large HDG’d parts have very rough uneven surfaces. That’s fine for chassis components that just go raw or get painted black, but it’s different with body parts. A new factory body panel will look great if prepped and painted, because the surface is perfectly smooth.

Here the many high (bright) and low (dark) spots of the uneven surface are visible.

And here I've highlighted several of the galvanizing buildup areas. These are only the obvious ones. Nearly every bit of surface is uneven to some degree. As soon as the surface gets any gloss from the paint, all the imperfections are amplified and showcased.

I supposed one could:

1. forget about the engine bay areas, floors, footwells, etc
2. sand down only the most offending zinc buildups
3. blast the while thing
4. apply primer
5. sand
6. apply high build primer
7. sand
8. apply filler
9. sand
10. apply sealer
11. paint

But that's a lot of work too, and I'd rather just have the metal flat than mask it.

 

[WreckITFrank]

makes sense, I have not painted anything galvy, but have seen the work of others including what you just posted. Appreciate you sharing.

 

[MountainD]

I have discussed this at length with one of my local Powdercoat folks called applied plastics. They said they could powder coat my bulkhead with a zinc impregnated paint that, although not quite as good as zinc dipped, has remarkable oxidation resilience and long-term anti-corrosive properties. It will probably be the path I will take if I choose not to do the legwork of sanding down as you mentioned, which I probably won’t do.

 

[WreckITFrank]

I have discussed this at length with one of my local Powdercoat folks called applied plastics. They said they could powder coat my bulkhead with a zinc impregnated paint that, although not quite as good as zinc dipped, has remarkable oxidation resilience and long-term anti-corrosive properties. It will probably be the path I will take if I choose not to do the legwork of sanding down as you mentioned, which I probably won’t do.

the local coaters offer something similar prior to top coat when doing wheels, i wonder if it's the same thing.

 

[MountainD]

I would think so, perhaps. In theory, I suppose it could work, but I have not done anything with my spare bulkhead yet---just sitting in my cool, dry garage taking up space.

 

[erover82]

After the three day marathon of grinding and sanding, it was time to prime, and quickly before the zinc oxidized.

Prep the epoxy, quick! Remember to clean up the bench later..

I don't have photos of what happened next, but image you've spent countless hours cleaning and sanding, the epoxy is ready to spray, you begin wheeling the bulkhead to the spray tent, the stand collapses because you're an idiot who didn't triangulate the frame, and the bulkhead crashes to the ground. I'm immediately thinking the whole trajectory of this project has shifted from making good progress, to a lengthy recovery and repair operation. However, upon examination it becomes apparent it landed it such a fortunate way that there were only three small points of contact and minor scuffing. My son and I repair the frame, hoist the bulkhead back up, clean the contact points of any contamination, and sand them with 80 grit.

We carefully resumed wheeling the recovered bulkhead into the paint tent and began the first coat. Here it is, wheeled back into the warm shop to cure overnight.

A few days later, back to hours of sanding, 180 grit this time. May I never lay another piece of abrasive on a bulkhead again.

Took a few days break to enjoy the PDX ABFM with my oldest.

The the dinner banquet with special guest Tim Hensley sharing photos and stories of his CT adventures was a great conclusion to a warm British motoring weekend.

OK, back to work. Laid down the second coat of epoxy. May have hand sanded it again, but I've lost track at this point. My dreams are filled with the contours of bulkheads.

A few days later I wheel it back out to the tent to finally lay down four coats of Light Keswick™. Fortunately, it turns out decent.

 

[gerken]

Did you test fit the bulkhead (and those new aluminum floor panels for that matter) before all the prep and subsequent prime and paint? Reading through this, I'm sure you did... but was wondering what that looked like, how the SP bulkhead mated up to chassis, other panels and sheet metal, etc. I'd hate to make such a great bulkhead statement only to drill through it later trying to bolt or rivet a stray hole that should be, but isn't.

 

[erover82]

Did you test fit the bulkhead (and those new aluminum floor panels for that matter) before all the prep and subsequent prime and paint? Reading through this, I'm sure you did... but was wondering what that looked like, how the SP bulkhead mated up to chassis, other panels and sheet metal, etc. I'd hate to make such a great bulkhead statement only to drill through it later trying to bolt or rivet a stray hole that should be, but isn't.

The strategy I used was to set the new and old bulkheads side by side to compare measurements and didn't find any major differences. I've drilled a few holes but that's the extent of my modifications. You're right though, fitting panels before paint often saves headaches.

 

[jymmiejamz]

We’ve definitely been burned before by not checking panel alignment before paint.

 

[gerken]

My post was a genuine question, definitely not a "..you really should have..." post.

I'm mainly curious because as I start developing strategies for purchasing new panels for my own Defender you start going down the deep, slippery review rabbit hole and it seems due to the manufacturing process from Land Rover, all the brands have their plusses and minuses.

 

[Greg_M]

I'd like to know how you've dealt with the potential for saponification with epoxy over zinc. I've had some issues in the past though on pieces much less precious than that bulkhead. It may never come up for me again but I'd still like to know. Thanks,

 

[erover82]

I'd like to know how you've dealt with the potential for saponification with epoxy over zinc. I've had some issues in the past though on pieces much less precious than that bulkhead. It may never come up for me again but I'd still like to know. Thanks,

Coating galvanized surfaces definitely requires careful process. Alkyd, oil, and even some so-called “epoxy” coatings are a waste of time on galvanized surfaces, often saponifying and flaking off within weeks. Saponification requires zinc, moisture, non-neutral ph, and various esters/fatty acids. A good epoxy primer will seal the surface, eliminating moisture transport, and thus eliminate the possibility of saponification. Also, the specific epoxy primer I am using, when applied to a properly cleaned and etched surface, is known to adhere well and without any saponification issues. Generally, whatever coating system is used should be verified to work well with galvanizing prior to application.

 

[supertreeman]

I'd like to know how you've dealt with the potential for saponification with epoxy over zinc. I've had some issues in the past though on pieces much less precious than that bulkhead. It may never come up for me again but I'd still like to know. Thanks,

Based on the rest of this thread, I think its safe to say however it was dealt with was:

1) The right way
2.) Better than how 99.9% of us would have

 

[Greg_M]

Based on the rest of this thread, I think its safe to say however it was dealt with was:

1) The right way
2.) Better than how 99.9% of us would have

That's why I asked.