Dichromate Dip Removal
09-01-2011, 04:04 PM
#2
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RE: Dichromate Dip Removal
Dipped Chromate finishes aren't just surface depositions like paint or electroplating. They can actually penetrate the surface of porous metals like Mg and Al to a (relatively) considerable depth.
I don't know if total removal is feasible. If the existing chromate is ratty looking, I'd just bead blast it and re-chromate it.
If you're going for a "bare metal" look, you might want to consider that the penetration of the chromate works to considerably reduce the reactivity of the surface metal and retards (not eliminates) the possibility of it starting to burn. A magnesium fire is pretty hard to put out. Its going to burn until it done, just like a LiPo fire does. Mg needs to be treated with a lot more respect than Al does.
My family was in the metal finishing business for 40 years. If you give a little more info in what your specific application and reasons for wanting to eliminate the chromate are, maybe I can be more helpful.
I don't know if total removal is feasible. If the existing chromate is ratty looking, I'd just bead blast it and re-chromate it.
If you're going for a "bare metal" look, you might want to consider that the penetration of the chromate works to considerably reduce the reactivity of the surface metal and retards (not eliminates) the possibility of it starting to burn. A magnesium fire is pretty hard to put out. Its going to burn until it done, just like a LiPo fire does. Mg needs to be treated with a lot more respect than Al does.
My family was in the metal finishing business for 40 years. If you give a little more info in what your specific application and reasons for wanting to eliminate the chromate are, maybe I can be more helpful.
09-04-2011, 10:30 AM
#3
RE: Dichromate Dip Removal
If the pan had even coverage of any kind I believe I would like it better than it sits right now.
The underside of the pan would either be polished or painted, but the inside I would like to see something of a more consistent finish without painting.
I might leave it as is, and mask off the Cox engraving and just polish that out for some detail. I'm just looking at lots of ideas still.
The existing coating is dry and almost non existent in some spots, other areas are very well treated and have a hard, gloss, non-porous dark coating of it.
What happens to magnesium if left untreated after grit blasting?
The underside of the pan would either be polished or painted, but the inside I would like to see something of a more consistent finish without painting.
I might leave it as is, and mask off the Cox engraving and just polish that out for some detail. I'm just looking at lots of ideas still.
The existing coating is dry and almost non existent in some spots, other areas are very well treated and have a hard, gloss, non-porous dark coating of it.
What happens to magnesium if left untreated after grit blasting?
09-04-2011, 03:33 PM
#4
RE: Dichromate Dip Removal
It's probably Aludine...
PdL (Philippe de Lespenay ) is quite well known in racing and slot car circles...(bad pun intended
)
I have used his methods several times on Cox Magnesium wheels and chassis (slot car ) parts...he worked at Cox in the 70's.
If you take a plastic tub and cover the part(s ) with "Scrub Free" it will work quite quickly...you can actually watch the corrosion bubble and lift off and form a scummy / bubbly layer on the top of the liquid in a matter of minutes.
I use one of those Glad or Zip Loc plastic (food ) containers with snap on lid...cover parts with "Scrub Free" cleanser and stay close by. Check on parts after just a few minutes...
Clean with a tooth brush (non metallic bristles ) and rinse w/ hot water...blow dry w/ compressed air.
I use Krylon rattle can clear coat to keep things protected.
http://www.electricdreams.com/Slot-C...gnesium-parts/
Edit: PdL doesn't recommend Lemon juice, but I have used it with good results. It works even quicker than Scrub Free.
One of those small grit blasters (made by Badger...looks like an air brush ) works well too...[8D]
PdL (Philippe de Lespenay ) is quite well known in racing and slot car circles...(bad pun intended
)I have used his methods several times on Cox Magnesium wheels and chassis (slot car ) parts...he worked at Cox in the 70's.
If you take a plastic tub and cover the part(s ) with "Scrub Free" it will work quite quickly...you can actually watch the corrosion bubble and lift off and form a scummy / bubbly layer on the top of the liquid in a matter of minutes.
I use one of those Glad or Zip Loc plastic (food ) containers with snap on lid...cover parts with "Scrub Free" cleanser and stay close by. Check on parts after just a few minutes...
Clean with a tooth brush (non metallic bristles ) and rinse w/ hot water...blow dry w/ compressed air.
I use Krylon rattle can clear coat to keep things protected.
http://www.electricdreams.com/Slot-C...gnesium-parts/
Edit: PdL doesn't recommend Lemon juice, but I have used it with good results. It works even quicker than Scrub Free.
One of those small grit blasters (made by Badger...looks like an air brush ) works well too...[8D]
