OzVMX Forum
Clubroom => Tech Talk => Topic started by: Rodpack on June 19, 2012, 06:59:52 pm
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Has anyone had any experience with blasted magnesium parts oxidising under a baked enamel finish and also under a powdercoat finish? I unfortunatly had the parts blasted before I found out that they have some sort of chemical treatment to prevent corrosion but was still surprised to find that painting and powdercoating didn't stop corrosion from happening and appearing through the finish. So does anyone have any tips for the treatment of mag parts? I've heard people talk about Dow#7 etc but never found a place that does that kind of work. Any help appreciated.
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Check out this article. Peter.
http://ozvmx.com/community/index.php?topic=22242.0
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I had my Magnesium Yamaha front and rear brake plates powder coated about 15 months ago in Precious Silver..Cant see any form of surface corrosion or imperfections as yet, in fact they look as good now as the day that they were done..Could be that the before process wasn't carried out properly.
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I did read that thread a while ago BYZ, that may have been where I heard about the Dow chemical treatment. So far I haven't found anyone who does it. Stinger, some people I know have had no problems with their mag parts after painting either, so I'm inclined to think that possibly the place that blasted and painted my parts may be the reason for my problem. The corrosion appeared in less then 12 months on my brake backing plates. On the powder coated brake backing plates it was a lot longer. I'm gonna strip them again and paint them myself and see how it goes from there.
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99.9% of paint/corrosion/adhesion problens are caused by poor cleaning/preparation......sounds like your problem.....remember with mag stuff to do the inside as well.
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If you use a thermally activated process (ie you bake it on) the gases in the material will come out and blow the finish and create all sorts of horrible oxidisation marks. Moisture then gets in and causes problems. My paint people(powder cost etc) leave the mag parts in the oven for a day before paint to drive out all the gases.
For a bit extra money they also treat the surface to provide additional protection (think t is a dichromate solution that is painted on, I can find out if reqd)
Worth the extra effort and expensive to protect the parts finish and make sure it stays on.
Mag loves moisture and will suck it up where ever possible and will fall apart infront of your eyes if you let it....
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Thanks Flower Pot, that sounds like a good explanation for what's going on. Leaving the parts in the oven for a day before painting is a good idea too. If you can find out what they treat the mag with that would be great. Where do you get your parts painted?
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Here is a link for the mag treatment.
http://www.chemical-supermarket.com/product.php?productid=421&send_isJS=Y&send_browser=YNY|MSIE|9|Win32|Y|1024|768|
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i also think there is places that do it, i know great sends his manx hubs off to some plater that does a diacromate ? gold treatment to them, think its electro boiled in like plating
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Thanks flyingdg, I ordered some of that product and I'll see how it goes. They only ship Fedex so postage stung a bit but I don't think USPS or Australia Post would've shipped it anyway.
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They treat it with a di chromate solution that is painted on and left to dry. I think it may be baked on. Gives a black (patchy) finish and holds the moisture back before the paint goes on. It isnt used to look pretty, they use it for additional protection before the top coat of paint is applied. Money well spent (it costs extra) if you want to give your parts that bit of extra protection