Sand blasting and magnesium

[Sankekur]

I have some parts that are magnesium that I want to strip the paint off of. Being magnesium I would prefer to keep away from chemical paint removal so sand blasting would be a good option, does anyone have any experience doing this or know whether it can be done? My concern being that the magnesium (this alloy at least) is pretty soft so I don't want to just cut through the metal.

 

[Auditor]

You'll need to find someone who does bead blasting. Much less abrasive and the medium of choice for magnesium car parts and covers. Just don't expect a shiny silver finish, as most of the time oil deposits will discolour the metal deeper than the surface. The surface will be clean though, but you won't end up with a shiny like-new piece.

 

[Sankekur]

Hmm, thanks for the info.
Luckily I am not looking for a shiny like new finish, I actually want the textured finish that sand blasting normally leaves on metal.

 

[Nic_s]

Sank, I know you know this, but for those that don't: From the bit of research I've done, you must repaint the parts to prevent corrosion. It's apparently quite bad if you don't.

I'm assuming this is cam covers your thinking of doing? I wonder if one could find aluminium replacements? Personally for me the magnesium is more effort than it's worth the 2-3kg it saves in weight.

 

[Mrcloc]

Buy some sandpaper and start slaving away. :rollsmile:

On topic with the title, for magnesium alloy wheels apparently the paint job is so solid that it's better to melt down the wheel and recast it.

 

[rick540]

My M5 Turbines were magnesium and I did a whole bunch of reading when I repainted them.

The short of it is, magnesium if bare will not form a protective oxidation layer like alu or stainless. magnesium just keeps corroding till it's all gone.

"Google magnesium preparation for paint" and see the insane process thay go through to get it prepared. That said I had my old cam covers chemically stripped powdercoated and they came out and lasted quite well

 

[Auditor]

Hmm, thanks for the info.
Luckily I am not looking for a shiny like new finish, I actually want the textured finish that sand blasting normally leaves on metal.

On a side note, the small sandblasting cabinets that you can buy for DIY use work very well. In fact it becomes quite addictive to sandblast small metal items because the result is so good and you get a good deal of satisfaction for your effort.

Generally the lower air volume these small cabinets work off, coupled with the fine aluminium powder you can buy for them means that very little metal is lost when you clean a part up. You'll obviously also have to buy a decent compressor, but once you have bought the whole kit you'll find plenty of stuff to sandblast. I really enjoy my set up. I've done everything from brake callipers to pliers in it.

 

[Sankekur]

Yup I am well aware of the fact that magnesium corrodes really fast....my plan in not to leave it unpainted......my only worry is the areas that I don't paint that will be in contact with the engine oil how it will react to that. It corrodes crazy fast in contact with water but not sure how it will be with oil.

@Rick: I came across a Magnesium treatment kit supplied by Henkel that can be used to prepare magnesium for painting or to prevent its oxidation.


I will see what I will do I have a spare set so maybe I will just try a couple of things on that first....though I have noticed that even where the paint has come off the magnesium hasn't started to oxidize.....I am wondering whether this isn't a more resistant alloy or maybe it has been diffused or surface impregnated with a type passivation layer or coating......hence also not wanting to damage the magnesium. I have found that the guys on the flood below us do glass bead blasting...specifically so they don't damage metal (they clean coating holders as far as I understand) so this is a plus.

 

[rick540]

Yup I am well aware of the fact that magnesium corrodes really fast....my plan in not to leave it unpainted......my only worry is the areas that I don't paint that will be in contact with the engine oil how it will react to that. It corrodes crazy fast in contact with water but not sure how it will be with oil.

@Rick: I came across a Magnesium treatment kit supplied by Henkel that can be used to prepare magnesium for painting or to prevent its oxidation.


I will see what I will do I have a spare set so maybe I will just try a couple of things on that first....though I have noticed that even where the paint has come off the magnesium hasn't started to oxidize.....I am wondering whether this isn't a more resistant alloy or maybe it has been diffused or surface impregnated with a type passivation layer or coating......hence also not wanting to damage the magnesium. I have found that the guys on the flood below us do glass bead blasting...specifically so they don't damage metal (they clean coating holders as far as I understand) so this is a plus.

Another consideration, whtever they use I found is very porous and retains oil even after several washes preventing any coating from sticking. The stuff needs to be soaked in cleaner for a few hours as well.

 

[Sankekur]

Yup I am well aware of the fact that magnesium corrodes really fast....my plan in not to leave it unpainted......my only worry is the areas that I don't paint that will be in contact with the engine oil how it will react to that. It corrodes crazy fast in contact with water but not sure how it will be with oil.

@Rick: I came across a Magnesium treatment kit supplied by Henkel that can be used to prepare magnesium for painting or to prevent its oxidation.


I will see what I will do I have a spare set so maybe I will just try a couple of things on that first....though I have noticed that even where the paint has come off the magnesium hasn't started to oxidize.....I am wondering whether this isn't a more resistant alloy or maybe it has been diffused or surface impregnated with a type passivation layer or coating......hence also not wanting to damage the magnesium. I have found that the guys on the flood below us do glass bead blasting...specifically so they don't damage metal (they clean coating holders as far as I understand) so this is a plus.

Another consideration, whtever they use I found is very porous and retains oil even after several washes preventing any coating from sticking. The stuff needs to be soaked in cleaner for a few hours as well.

What cleaner did you use? An ordinary solvent based cleaner?

 

[ters]

Another option is soda blasting.
Benefits from soda blast: http://www.sodablast.co.za/what-is-soda-blasting/the-benefits.html
Companies: http://www.sicblast.co.za/
or DIY: http://www.aircooledtech.com/tools-on-the-cheap/soda_blaster/

Browse through the SIC blast site for pictures on results. :thumbs:

Ters.

 

[applehero]

Speak to Zaleonardz - think he has some sort of "baking soda blaster" to clean parts. That may be less abrasive

 

[rick540]

Just did a tappet cover today with soda blasting, perfect

 

[Sankekur]

Started glass bead blasting the stuff on Friday seem to work pretty well.

Unfortunately the blasting seems to take off the passivization layer (something chromate or other) as well so I will have look into that as well.

 

[rick540]

Any idea where one can buy the blasting media in CPT? I cant seem to find

 

[Auditor]

Blastrite are the people that manufacture and import all the available blasting media, the Capetown number is 021 417 1700.