Magnesium Wheel

[pancho villa]

Just ordered tires from M&S should be here on next delivery, now I must prep wheels, is sand cloth recommended, 500 then 10000 grit.
Also cleaning agent, I like Mothers, but would this work on my mags.

[pancho villa]

  going for a look like this

[Cornpanzer]

Looks like two silver painted wheels to me. One with old paint and one with new paint. Neither of those is bare mag.

[pancho villa]

this fellow is the man, I don't know how to link his page to here but he breaks it down.

stevekouracos.wordpress.com/restoration/.../aluminum-magnos

I goggled magnesium wheel restoration,    very useful information.     

[John Palmer]

Campagnolo wheels were coated originally on Pantera's.  It looked sort'a like the DOW Coating on the old Halibrands, as I remember?  You need to remove the coating first, if your going to polish, then deal with the oxidation.

[Jon]

Are you going to use these Lambo wheels mr Villa?
Those are beautiful, but a bit of a hassle to get mounted?
They do look great in dull gold as well.
Thumbs up!

[gizago]

He has a Lambo to mount them on  pics in his build thread.

I think the original finish was painted on these rims.

[hotrodsurplus]

Pancho, be very careful what you ask for. Surfaces with many defects look terrible when polished and it would be hell on earth to eliminate the pits in those intricate castings (which look beautiful the way they are). And once you polish magnesium you will have to re-polish it on a nearly weekly basis. I know this. I had polished magnesium wheels (Halibrand). They are much simpler than yours and I HATED maintaining them. It would not be so bad to polish the ribs and edges of your wheels though. You would still have to polish them frequently but it would not be so bad.

It is not a good idea to paint directly over bare magnesium. Older magnesium alloys contain a lot of iron. Iron is very noble compared to magnesium. Magnesium in the presence of iron and oxygen corrodes rapidly. It is the reason that magnesium is used for sacrificial anodes to protect steel. The metal will actually corrode under the paint. When you strip the wheel it will look like worms crawled around on the surface. 

You have to passivate the alloy so its elements do not react in the presence of oxygen. That is what Dow 7 and Dow 19 do. Those are what are referred to as chromate conversions. They convert the surfaces so they do not react. But the coatings are not permanent surface finishes. They were designed to be painted over or protect a surface for a short time which explains why the gold tone on Volkswagen engine cases fades in time. That was merely to protect cases during the machining and shipping process.

It is very difficult to find a shop that will treat parts with Dow 7 or 19 even in Seattle and Los Angeles where the aerospace industry is big.

There is another (and probably better) option. Henkel makes a spray-on conversion coating. It is intended for touch-up work but I imagine that it would work on a whole wheel. Henkel products are available worldwide.

http://www.henkelna.com/cps/rde/xchg/henkel_us/hs.xsl/product-search-1554.htm?nodeid=8797998120961
http://www.chemical-supermarket.com/Magnesium-Treatment-Kit-p421.html

Yes, sanding is a good option for mag but for your wheels I would recommend blasting with soda or glass beads at a very low pressure just to clean the surface. Mag is very porous and high pressure will force undesirable contaminants into the surface.

You do not have to paint magnesium. You can leave it bare if you coat it with wax or oil. These are my current Halibrands a year after I sanded them and rubbed regular automotive wax on them. I sprayed WD-40 on them since then. That was more than a year ago and I drove the car a lot. Even in the rain. They look about as bright as the day I sanded them. If you leave them absolutely naked for a few months they will turn a beautiful dark gray. Then you can seal them with wax or oil and they will stay that beautiful gray forever. I think they would look killer if you let them turn gray and then polished the lips.

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[Jon]

He has a Lambo to mount them on 

That is the best place for them   I would love to own a set of them

[UltraOrange67-2443]

FOR SALE! Un-used LP400 Wheel

[Straight Time]

Just read the restoration techniques from the thread Poncho Villla posted. Here
   
http://stevekouracos.wordpress.com/2012/04/25/aluminum-magnesium-wheel-restoration/


This guy states not to use Zinc Chromate Primer .  Any reason why ?

I know from advice on the lounge before that this was recommended and is what Porsche used on O.E.M Mag wheels i.e Gas Burners.


Ta

[Straight Time]

Sorry.....


Pancho Villa 

[Straight Time]

Anyone  !! 

[hotrodsurplus]

This guy states not to use Zinc Chromate Primer .  Any reason why ?

I know from advice on the lounge before that this was recommended and is what Porsche used on O.E.M Mag wheels i.e Gas Burners.

Okay, I'll take a stab at it.

First off, the five gas burners that I bought in the early '90s (because they were half the price of Fuchs, fancy that...) came in their original silver coating. I stripped the wheels myself. There was absolutely no zinc-chromate primer on them. There definitely was a hint of Dow 7 or alodine under the paint, however. After I stripped the wheels (chemical stripped by the way) the wheels looked a lot like an old Volkswagen or Porsche case. They were slightly brownish-gold with dark streaks wherever the paint failed. I'm not saying that all wheels were done that way but the ones I had were. And they were virgins.

I think he discourages using zinc-chromate primer with the alodine because both are types of conversion coatings. They function differently from each other, though.

Oxygen is highly unstable and reactive. It always wants to pair with something else, which is why oxygen atoms are generally seen in pairs. When it pairs with relatively unstable iron, for example, it blows electrons from the iron molecule and the new union becomes iron oxide, AKA rust. Well the same thing happens with magnesium (and aluminum and other metals) depending on their stability.

What alodine does is combine the vulnerable metallic molecules with hexavalent chromium. The hexavalent chromium basically completes the metals' electron structure. Since the metals are now complete electrically the oxygen molecules can't combine with them. That's what they mean when they say alodine is a conversion coating. It converts the surface to a stable form that isn't as vulnerable to oxidation.

Zinc chromate, on the other hand, is basically a coating made up with a chemically altered form of zinc. Rather than forming molecular bonds with the vulnerable metals it creates a film coating. Zinc is sacrificial--it will sacrifice itself to protect the metal below it. So doing both may be excessive. I don't know if it would cause any harm but I have heard of aircraft people priming alodine-converted parts with zinc-chromate primer.

As far as priming goes, a good friend and PPG rep beat it into my head that it's not a good idea to apply epoxy primers like PPG's DP series over etching primer. I don't feel like an hour-long conversation with him so I'm not going to call. Next time I talk to him I will ask, though.

From my understanding the very best course of action with mag is to strip the metal, immediately convert it with an alodine passivation, and follow that as soon as possibly with epoxy primer. But consider the source: I just wax my mag and let it darken over time. The dark finish will not harm it. The white crusty stuff that develops will definitely destroy mag.

[pancho villa]

Well spoken young man.

Just received word from my pal that my wheels where painted.
I hope their nice I will post a few pics soon.

[Straight Time]

Hotrodsurplus,

great reply thank you.

My Gasburners have a green type undercoat on them and just assumed this was factory applied.


What would be the best way of restoring the rims. I have some pitting on the rims where they were  previously polished and not coated. I have tried to lightly sand them down but the pitting seems to get worse.

Any tips.....

[Sarge]

I got my fill of magnesium polishing with early Berg intake manifolds, BRM's on the Underdog and later with a set of Halibrand spindle mounts.  Keeping magnesium shinny takes a butt load of
ELBOW GREASE!  Looking at Pancho's Campy wheels is downright scary; best to take Hotrodsurplus' advice with media blasting and letting the metal return to grey... there's too many bumps,
grooves, ridges and openings to hand sand and polish (all times FOUR!!).  I remember all too well spending the bucks to have Sihilling Metal Polishing do the Halibrands up to a beautiful luster
before mounting them up on the front of our sand rail.  They turned dull grey from the exhaust of our truck on the first tow out to the dunes ... who'd a thunk it??

[dyno don]

...AHHH...The notorious "Jim E." buggy returns....  Sarge, i remember hearing about your tear jerking buggy when I worked at Auto haus back in 72/73?     Made quite an impression way back then as is does once again after seeing the pic.  SWEET..!!  Always liked 'Hali's'....   Keep on Rockin' ya retireeeeeee....Hic,burp, $%^&*......(pretty please) save me a beer..!!   Mag wheels...no thank you...after owning over 22 sets of the famed BRM's at one time I can tell you ALL firsthand that after polishing and keeping up I couldnt even pick a decent booger afterwards.

[hotrodsurplus]

Thanks for the props, guys. I appreciate it.

My Gasburners have a green type undercoat on them and just assumed this was factory applied.

It very well may be. Mine may have been altered or made at a different time than yours.

What would be the best way of restoring the rims. I have some pitting on the rims where they were  previously polished and not coated. I have tried to lightly sand them down but the pitting seems to get worse.

Okay, I just talked to my PPG rep, Andy Ganderton. I've worked with him for close to 15 years. He's a hot rodder so he knows the products and how they apply to our cars. He's been in the industrial coatings department for quite some time so he knows the really creative stuff. Here's what he recommends.

He says if you can get away with just sanding the surface then that's probably the best prep. HOWEVER, he says if there's evidence of any oxidation or pitting or if the design has tight nooks and crannies then sanding alone will not be adequate (in other words, sanding alone won't work for us).

He says to first blast the surface with CLEAN glass or walnut media at as low a pressure as possible. I recommend glass because it will better dig out the oxidation in pits.

From this point he recommended three options. The order that he offers is technically the most correct by the book but it's not necessarily the order he prefers. In fact the method he prefers most is the last one. It's also the simplest one that any of us can do without special equipment.  

Option 1:
After blasting the parts take them to a shop that does Dow conversion coatings and have them dipped. He says you may not be able to find a shop that will work on old equipment, especially if you are a private party and not a business. Once you get them home then quickly wash them with wax-and-grease remover like DX330 and immediately prime them with a good-quality high-wetting epoxy primer like DP-series primers. He says any color will do but it's a good idea to choose a color that closely resembles the finish color. He says you may fill them with whatever plastic filler you prefer if you need to smooth the surface. From there paint them with a two-part paint. As long as you don't intend to color sand them then you can use a standard two-part single-stage metallic (formulated to work without a clear coat).  
 
Option 2:
After blasting the parts them prep them with an alodine conversion like the Henkel product. He emphasized to make sure that the alodine is compatible with magnesium. He says that some alodine treatments are formulated for aluminum and will react with the mag. But he says so long as the label indicates the alodine is for magnesium then you should be okay. From there he recommended following the procedure from the first process (wax/grease remover, priming with epoxy, and finishing with two-part urethane).

Option 3:
Andy prefers this method. He says it's the least effort and the least cost and based on his experience it will protect the mag just as well as the other methods for what we intend to do with these parts. He says it might be a different story if we were using these parts on an aircraft or boat but that for a car wheel it would be more than adequate. He did emphasize that these steps must all occur immediately after the other.

After blasting the parts then IMMEDIATELY wash them with wax-and-grease remover and a Scotch-Brite pad. He says that blasting will push oxygen deep into the pores and that it can induce oxidation (the conversion processes above eliminate the oxygen when they convert the finish). He says to force dry the parts and the instant they're dry then apply the epoxy finish. He was adamant about coating them as soon as absolutely possible because like with aluminum oxidation sets in instantly on magnesium. From that point finish the surface with the same filler/two-part urethane paint from the other two options.


About zinc-chromate primer. He says that the term zinc-chromate primer is more of a marketing term than an actual composition anymore. The zinc-chromate finishes of today do not offer near the same protection as the ZC finishes did even a decade ago (a dozen years ago Andy gave me a gallon of 'banned' PPG ZC when it had to be cleared out). He says that as far as he knows no ZC primers are catalyzed. That means that they are not as tough as catalyzed finishes. He does not recommend them for anything unless they're formulated for a specific application (which doesn't apply to us).

About etching primers. He says he would not use an etch primer on a mag surface, even if it's been converted. Etching primers are acidic and he says since it's near impossible to determine the PH you are likely to do more harm than good by applying etching primers to reactive surfaces like mag. On aluminum and steel he says it's not such a critical issue because they are a lot more stable than mag.

About epoxy primers over etching primers. He says that it is safe to apply epoxy primers over non-pigmented (clear) etching primers because the acids purge from the finish during the curing stage. The problems arise when applying epoxy primers over pigmented (opaque, colored) etching primers. He says that the pigments are either acidic or retain trace amounts of the etching acid after the etching primer cures. That's a problem because epoxy primers use an alkali solution. In other words, epoxy primers are basic. And we all learned what acids and bases do when you combine them. He says that the epoxy primer and pigmented etching primer will gum up and come off in sheets and it's very difficult to strip the mess.

He concluded by saying that we are probably over-thinking the whole process. He says as long as we isolate the surface from oxygen that the magnesium will not oxidize. He says the most important part is coating the surface immediately after prepping it. According to him, the magnesium won't just destroy itself even if the coating is less than ideal. Case in point, my '50s Halibrand wheels had mud tires, came off the back of a '70s Ford pickup, and wore a few hastily applied coats of aerosol paint. That's about as bad as you can get and those wheel are just fine today. In fact they still aren't painted. I just rub them down with wax and wipe them down every once in a while with oil. You see how silvery they are.

So there you have it from the horse's mouth.

[richie]

My Gasburners have a green type undercoat on them and just assumed this was factory applied.

All the ones I have had that werent messed with had the green coating under the silver,I think it is a factory coating/etch undercoat

cheers Richie

[hotrodsurplus]

My Gasburners have a green type undercoat on them and just assumed this was factory applied.

All the ones I have had that werent messed with had the green coating under the silver,I think it is a factory coating/etch undercoat
cheers Richie

That's the zinc-chromate primer we talked about earlier in the thread. It's not an etch at all. It's just a primer that merely sits on the surface and sacrifices itself to protect the metal it's applied to. It serves the same basic function as galvanization only it's sprayed on rather than deposited by electrolysis.

If you flew a bomber during WWII Rosie the Riveter was the most beautiful woman in the world. Here she is drilling a fuselage spar that's been coated with zinc-chromate primer. This is more yellow but ZC can also be brown or green depending on the formula.
http://i412.photobucket.com/albums/pp202/ruspren/ZCyellow.jpg

Actually here's the inside of a quarter panel that we peeled off of a '66 Chevelle last Monday. There was zinc-chromate primer all over the inside of the panel and the outside of the wheel house. Also a bunch of panels behind the rear wheel well were galvanized. I was really quite impressed.
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[Straight Time]

Great info. I think the quote about us overthinking the process is applicable .

[ibg]

that yellow stuff in the bottom pic look like cavity wax, another good panel preserative

[hotrodsurplus]

that yellow stuff in the bottom pic look like cavity wax, another good panel preserative

Definitely 100 percent absolutely not wax. It's zinc chromate. Once you accidentally hit the stuff with a grinder you never forget the way it smells (it's really toxic so avoid doing that at all costs). It's on the outside of the wheel house and the inside of the quarter panel.

[pancho villa]

well I had a pal paint my wheels he did a good job, a lot better than my attempt was turning out.

[Sarge]

Nice work!

[pancho villa]

thank you sir, its a two foot job,    looks really good from about two feet

[henk]

that yellow stuff in the bottom pic look like cavity wax, another good panel preserative

Definitely 100 percent absolutely not wax. It's zinc chromate. Once you accidentally hit the stuff with a grinder you never forget the way it smells (it's really toxic so avoid doing that at all costs). It's on the outside of the wheel house and the inside of the quarter panel.

yes that is zincromate it is the only stuff that protect and seal magnesium of from the air.
it is also used on magnesium parts on aircrafts.

henk!!!