I just picked up a used System One roof rack for the van. For those who may not remember, the van is pictured below.
The rack is well-used and dirty, but I didn't find any corrosion (the white crusty stuff) anywhere on it. I don't want to install a bare aluminum rack on a red van with bronze wheels so I was going to maybe powdercoat it bronze like the wheels to tie it in. Black is also an option since I'm blacking out all the chrome on the van, but I don't really want to get second degree burns in the summer while camping up there or when loading some lumber.
Anyway, looking at ideas for making it bronze. Powdercoat was my first thought, but will that make the t-slots unusable? I suppose I could do the orange phosphorus acid stuff and paint it, but not sure how paint would hold up to abuse.
The van:
The rack (stock photo)
Scotchbrite, alodine, powdercoat.
Powdercoat shouldn't be any thicker than paint.
You could anodize.
Back when I worked as an HVAC rep, we had aluminum linear diffusers anodized by a local finisher. It wasn't cheap, and I suspect with environmental regs, it hasn't gotten any cheaper. I think there was a substantial set-up charge also.
Soda blast would likely work well to prep for paint.
84FSP
UberDork
9/19/22 1:04 p.m.
I always used fresh blast grit and then plastic bagged the part to keep hand oilds and muck from getting on it. Huge fan of powdercoat.
jgrewe
HalfDork
9/19/22 1:14 p.m.
When doing older aluminum I would lightly blast the parts with aluminum oxide paying special attention any pitted areas. You can also use Ospho for prep but I like the surface a little roughed up.
I would then outgas the parts by taking them up about 20 degrees hotter than the powder cure temp and hold them there for about 20 min. That will burn any oils or solvents out that might cause trouble later during the lower temp cure.
If pitting isn't that bad you can hit it with a sandable powder primer. The primer can be tricky when you go to do the top coat but if you preheat the part to about 250F the top coat will build easily.
If the pitting is really bad you can use JB weld. It won't be structural but it will survive the heat enough to fill pits.
Your t-slots could be an issue if they are really tight fitting. Powder builds to about 4mils. If they are tight before powder you can clean the powder out of the slot with compressed air before baking. I would run a small nozzled gun down the length of the track and gently blow it out. The other option would be to tape the slot off with high temp tape.
I'd probably go with blasting and powder coating as well. Worst case, you have to grind the T-slot nuts down a little so they will slide easily.
The slots are pretty tight, but I think I can keep the powder out of them. Maybe a strip of 1/2" foam weatherstrip stuffed in there to spray the powder and remove before baking. I have a buddy who is hooking me up with the powder coating for cheap, so I assume he'll have some ideas as well.
So far I haven't found anywhere that the anodizing has been compromised. No pitting or white corrosion. If I don't have access to soda blasting, is there a chemical treatment I could do first instead that would work as well? (translated: I was quoted $400 to soda blast it and my wallet is a bit skinny)
triumph7 said:
Scotchbrite, alodine, powdercoat.
Powdercoat shouldn't be any thicker than paint.
You could anodize.
Is alodine the orange phosphorus stuff? And is that different than Alumabrite?
jgrewe
HalfDork
9/19/22 5:38 p.m.
If one of these will fit into the slot just coat the whole thing and blow out the slot before baking. You will be surprised how surgical you can get. If you take too much off just re-dust that area and try again.
Spent a few hours today with soapy water and a scotch-brite. A few sliced knuckles later and a few more google searches has me back.
The dirt cleaned up nicely. The aluminum is stained a bit, but not bad. Just wondering how far I have to go... that is, how much cleaning I need to do. Do I need to get those stains completely off? Am I trying to get rid of the anodized surface? Or am I just degreasing and scuffing for grip?
In lieu of soda blasting, what about burnishing it with a wire wheel on a grinder?
If I end up painting (or powdering), I noticed most google results using either Alodine OR self-etching primer. Once I Alodine it, do I need self-etch or is that redundant?
Another product I noticed was Alumaprep 33 (also called Bonderite 33). That step also says it brightens aluminum. Is that product the same as aluminum brightener? Is it necessary? Recommended? Feel free to go all chemistry on me, I'm good with that. I'm curious why the Bonderite 33 is $60/qt vs aluminum brightener for $30/gal. If they are the same thing, can I save some bucks?
Curtis73 (Forum Supporter) said:
Spent a few hours today with soapy water and a scotch-brite. A few sliced knuckles later and a few more google searches has me back.
The dirt cleaned up nicely. The aluminum is stained a bit, but not bad. Just wondering how far I have to go... that is, how much cleaning I need to do. Do I need to get those stains completely off? Am I trying to get rid of the anodized surface? Or am I just degreasing and scuffing for grip?
In lieu of soda blasting, what about burnishing it with a wire wheel on a grinder?
If I end up painting (or powdering), I noticed most google results using either Alodine OR self-etching primer. Once I Alodine it, do I need self-etch or is that redundant?
Another product I noticed was Alumaprep 33 (also called Bonderite 33). That step also says it brightens aluminum. Is that product the same as aluminum brightener? Is it necessary? Recommended? Feel free to go all chemistry on me, I'm good with that. I'm curious why the Bonderite 33 is $60/qt vs aluminum brightener for $30/gal. If they are the same thing, can I save some bucks?
Anodizing is an etch that controls corrosion and helps paint adhesion. I suspect the other chemicals you mentioned are similar.
jgrewe
HalfDork
9/19/22 11:32 p.m.
If you are going to powder it just soak it with Ospho for about 30 min then rinse well with water. If the Ospho dries, re-wet it with Ospho then rinse with water.
It will be etched and ready to go once it dries.
