SiWhite Posted February 16, 2010 Share Posted February 16, 2010 I've just got my door frames back from being shot blasted prior to their trip to the galvanisers. Horror of horrors, some of the joints in the frames appear to be brazed together. I called the galv company and thier answer was predictable - the brazed joints will fail in the tank and I'll only have half my doors left afterwards I wanted them galv'd so I'd never have to worry about corrosion (especially internal) again, and so don't mind paying for the right process. Can anyone suggest alternatives that will coat the inside of the frames? I think zinc spray will only do the outsides. Should I weld the brazed joints together instead? Quote Link to comment Share on other sites More sharing options...
Aragorn Posted February 16, 2010 Share Posted February 16, 2010 what about "e-coating" or even zinc electroplating rather than hot dip? Quote Link to comment Share on other sites More sharing options...
Rich_P Posted February 16, 2010 Share Posted February 16, 2010 Gallons of paint and then waxoil, followed by a rubber barrier between the alloy and steel? Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted February 16, 2010 Share Posted February 16, 2010 the zinc spray is highly underrated Quote Link to comment Share on other sites More sharing options...
jcwcooper Posted February 16, 2010 Share Posted February 16, 2010 Ive no idea what its called but the guys in VW scene use it (beetles campers ect) its a light brown coating that the vehicle is dipped in and an electrical charge is applied, apparently its used on modern cars.......but like i said no idea what its called. I saw it on Beetle crisis Dave. Quote Link to comment Share on other sites More sharing options...
SiWhite Posted February 16, 2010 Author Share Posted February 16, 2010 the zinc spray is highly underrated But I guess it can't do inside door frames? Quote Link to comment Share on other sites More sharing options...
Aragorn Posted February 16, 2010 Share Posted February 16, 2010 Ive no idea what its called but the guys in VW scene use it (beetles campers ect) its a light brown coating that the vehicle is dipped in and an electrical charge is applied, apparently its used on modern cars.......but like i said no idea what its called. I saw it on Beetle crisis Dave. Thats the e-coat i mentioned above. SPL do it, amongst others. http://www.surfaceprocessing.co.uk/ Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted February 16, 2010 Share Posted February 16, 2010 Simon I really think there are no real alternative to galvanising and understand your pain. But if it is possible and you are up for it, I think you should weld the parts together. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted February 16, 2010 Share Posted February 16, 2010 There is no treatment as effective as Galv from the point of view of coating the interior of the frames. I would take Soren's advice and weld the joints - you would only need a few short bits of weld just to make sure they stay together in the galv bath. Second choice would be electroplating and waxoil, but it is a distant second place. Quote Link to comment Share on other sites More sharing options...
simonr Posted February 16, 2010 Share Posted February 16, 2010 Hot Zinc spray (spraying with molten zinc) is very good and gives a good surface for paint or powder coat to key to. OK it will not get right inside closed sections - but the zinc acts as a sacrificial anode and affords protection to the areas not covered (to some extent). The most important thing though is to electrically isolate the Aluminium from the steel. The current flow between the two is one of the biggest causes of corrosion in Land Rovers. Thick insulating tape works pretty well. Si Quote Link to comment Share on other sites More sharing options...
English Gent Posted February 16, 2010 Share Posted February 16, 2010 A sacrificial anode system generally only works when submerged in an electron carrying solution (sea water, for example) so a uniform coating is your only real option as even a small gap in the coating would act as a corrosion pit for the beginnings of rust. If the steel frames are sealed tubular sections, then you will likely suffer pressure build up during insertion to the zinc bath resulting in possible distortion. Exposure of the brazed joints may result in the braze (tin, copper?) melting out at the elevated temperatures, so if you really want to have internal hot dipped zinc then you're going to have to weld the frames. If however you're not completely stuck on hot dipping thin walled components, then a good second would be to abrade the sections back to bar metal and bush apply a substance called 'zinga' to the outside of the frames, and use a chassis treatment hose sprayer to apply lots and lots of waxoyl to the inner frames. I did this with my replacement bulkhead and it was still perfectly solid when the old lady went. As has been mentioned, you should insulate the alloy door skin from the steel frames as this in itself will set up a galvanic reaction whereby ion transport from anode to cathode (or the other way round... it's been a long time since I was studying corrosion mechanics) starts the breakdown of the alloy skin. This insulation can be achieved with thin rubber, wide insulating tape or even thick paint. I think Frost's use to sell body sealer for just this sort of application. Quote Link to comment Share on other sites More sharing options...
pinny Posted February 16, 2010 Share Posted February 16, 2010 as its been said hot zinc spray or hot aluminium spray when i left school i worked as a shotblaster paint sprayer we also done hot zinc and aluminium spraying the beauty with this you can put what thickness you want on usually about 150 microns a lot of navy stuff was metal sprayed my uncle has a factory in witham essex i know your a fair way from here,chris. Quote Link to comment Share on other sites More sharing options...
ajh Posted February 17, 2010 Share Posted February 17, 2010 Epoxy paint dip is also viable if you can find someone who does it, I know ECR does this for their rebuilt doors. Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted February 17, 2010 Share Posted February 17, 2010 Si, they're not too hard to weld up without distorting them. If you bring them up to me I'll tickle them with my MIG before you send them off, if you like? Quote Link to comment Share on other sites More sharing options...
will_warne Posted February 17, 2010 Share Posted February 17, 2010 Si, drill a hole to open up the closed sections, electroplate and then isolate with duralac. Job done. Quote Link to comment Share on other sites More sharing options...
SiWhite Posted February 17, 2010 Author Share Posted February 17, 2010 Thanks for the thoughts guys. I'm going to have a go at MIG'ing them this weekend. Bit worried about the brazing rod stuff contaminating the weld, but we'll see. Galving them is still the plan as long as they can be welded, as I've got a load of other stuff to do at the same time. The new skins I have ordered are steel as well, so hopefully there won't be any electrolytic corrosion problems. Quote Link to comment Share on other sites More sharing options...
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