Headlamp refurb

[CJH]

A couple of years ago I bought a twin headlamp conversion kit, complete with grille, badge, inner spotlights and mounting brackets. The inner spotlights seem to be pukka Hella units, but I'm not impressed with them. I noticed very quickly that one of them was letting water in around the joint between the glass and the metal reflector. That one was replaced free of charge. The other one, and the replacement, both seem to keep water out, but nevertheless one of them has rusted badly in just over 18 months.



As far as I can tell, the corrosion started at the sharp edge of the metal reflector, and then worked its way in under the chromed surface, so the integrity of the seal to the glass isn't the issue. If I buy any more I'll run some additional sealant round the edge to cover that sharp edge.

As you can see in the photo, half the reflector has rusted - this seems to be the chromed surface itself that's rusted - and then in addition a fair amount of the metal backing has rusted and pitted quite badly.

When I bought my powder coating kit I also bought some 'high chrome' powder, so I thought I'd have a go at refurbishing this reflector. I started by using a flap wheel in a Dremel to remove the original chrome surface.



Note the cream coloured undercoat/primer between the metal frame and the rusted reflecting surface in the shot above, confirming that it's the reflecting surface itself that's rusted.



I then had a go with the chrome powder coating. I was quite pleased with the finish, but something in the pitting must have reacted with the powder coating - I guess the flap wheel didn't get right into the pitting.



So I grit blasted the whole thing back to bare metal, to make sure I'd removed all traces of the original surface from the pitted area.





This time it didn't react, but the powder coat didn't smooth the pitting as much as I was hoping - in the oven it flows a little when it melts, but obviously the pitting was too much for it to cover. If I do it again I think I'll use some high temperature undercoat and perhaps try to sand out the pitting a bit. But it's still a fairly good reflective surface, and I figured that behind the textured glass lens it probably won't show.

Here's a side by side with an original reflector - the one that was replaced when water started getting in. Note that the original surface is *very* delicate - you can see a lot of fine scratch marks that I made when I attempted to remove traces of water droplets using only a spectacles cleaning cloth.



And here's a shot of the original with bulb and glass, followed by the powder coated version with bulb and glass.





I'm quite happy with that. I'm not sure whether the heat in the lamp will affect the powder coating, but i'll soon find out. And if the metal does start to corrode again, at least it won't be the reflective surface itself that corrodes.

[itchyfeet]

Looks good Chris

[bigherb]

That powder coat is quite impressive.

[CJH]

That powder coat is quite impressive.

Yes, it's quite amazing how a dull grey powder results in a chrome finish - I have no idea how. The finish is not very resilient, and if you scratch it it shows black underneath, so they recommend you coat it with a clear powder coat. But that turns it a bit milky, and I figured resilience isn't needed inside a headlight. I'm more worried about whether the finish will melt from the heat - it has to be cured at 180º, but probably softens a bit below that temperature.

[CJH]

I connected the lamp up to a battery and ran it for 25 minutes or so, then checked some temperatures with a temperature probe on my multimeter. The bulb itself got up to about 300º. The glass immediately in front of the bulb reached just over 100º, but at the edges it was no more than about 50º. The reflector itself seems to have done what reflectors do best, and reflected the heat onto the glass - even close to the bulb it was no more than 60º.

I imagine that after a longer period the heatsoak from the glass in front of the bulb would raise the temperature at the edges a bit further, which might then conduct heat to the metal reflector. But this was a static test indoors - on the van it'd be cooled by airflow, and this is a spotlight, so not usually on continuously for anything like 25 minutes.

The beam pattern looked good on the ceiling, so I reckon it's worth bonding the glass back on and giving it a proper test on the van.

[kevtherev]

Do you think the finish would have been improved by polishing the reflector?

[CJH]

Do you think the finish would have been improved by polishing the reflector?

After grit blasting and before powder coating you mean? Possibly, but the powder coat seems to smooth out the tiny imperfections that you get from grit blasting. The area where it didn't is where there was rust pitting. Maybe some mechanical sanding/polishing would have got that smoother. There is a high temperature base coat spray that the powder coating company sell, but I've never tried it. It might act as a bit of a filler to help with smoothing.

I'm toying with the idea of sanding the existing chrome powder coat a bit smoother and then adding another coat, but really it isn't visible under the glass - I might do more harm than good.

[kevtherev]

Yes before the coating
I have worked in high lustre powder coat on plastics and although the surfaces were not polished they were VERY smooth.
I can see that the coat is thick and does indeed look 100% better.
Im just being a perfectionist