I thought a quick check on painting Mag wheels would be good. I know etching them can be a bad idea depending on what sort of alloy is used.
Found this
"Ok its an old post.. but just to help.. I refurb wheels, have done for a long time now, magnesium wheels are a complete bind.. and there's no easy answer, a lot of companys won't touch them and with good cause. magnesium as we all know is very unstable and oxidises very repidly when in contact with air/ water/ salt/ acids.. the process to redo them is not quite as straight forward as acid strip etch prime and powdercoat!!
firstly yes you have to be VERY wary of acid stripping, it has to de done, however the timing is critical.. stripping acid will not only etch magnesium badly, but will also soak into the metals pores, they have to be bathed and bathed and bathed and soaked in alkaline solution before the next stage!
bead blasting, this has to be done at a low pressure as magnesium is a soft and easily damaged metal, also the risk of blasting any residues deep into the porus structure of the wheel is an issue..
after the blasting stage the true extent of corrosion is VERY evident, particularly where wheel weights have been attached.. I have seen 50% + of the actual stock completely gone where the weights have been!!, the other prime damge area is where the brake disc sits, you tend to get 2 big grooves where the brake dust has been thrown out from the pads on either side of the disc, I'v seen this so bad before that its almost rotted the wheel into two pieces!!.. at this stage you have to decide if the wheel is even safe anymore..
next comes a process called out gassing.. most wheel restorers wont even know about this and wonder why when they paint the wheels big air bubbles appear.. magnesium creates gas.. deep in the pores.. when sealed in it will build up and pop up big air blisters.. the answer is to heat them, allow them to cool and paint them immediately!!.. this will 99% stop the problem..
corrosion removed and structural integrity ascertained you then etch prime, high build prime, and paint either with powdercoat (cheap and in my opinion not recomended for mag) or a good 2k base and clear..
job done.. problem is that even the slightest contamination, or chip or scuff will set the mag off again.. basically mags are an ongoing problem and to my best knowledge cannot ever be gauranteed to last problem free for years..
so there you are.. the (I think) definitive answer about mag wheels.. personally I hate doing them, I mainly do ferrari ones and maserati, chromadora's and campagnolo's, and frankly the results can be dissapointing, as even though structurally sound the end result invariably shows some level of deep pitting..
steve
grindnshine.co.uk"
And I have nothing to do with them at all.
Mind you, do we ever get to the point where our mag wheels have ten years of corrosion or even five years of life.
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spray painting alloy wheels by 'buzzinrussell' (22 Jan 2010 @ 15:46)
