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aluminium crank cases

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gerry madden09/06/2017 15:45:36
140 forum posts
55 photos

Hi, I have some aluminium crank cases from a small engine that have been in a damp environment for a few years and have developed that patchy white dusty coating.

I'm sure it will rub off with a bit of effort but I'm just wondering if there is a much more efficient way of cleaning these things up without leaving abrasive scratching marks in all different directions ?


Jeff Dayman09/06/2017 16:00:05
1915 forum posts
45 photos

You might try a motorcycle engine repair shop for glass bead blasting. It will leave a nice clean matte finish on your aluminum and not mar any details or leave scratches.

A coat of good clear car wax afterward, or some clear urethane spray clearcoat on outer surfaces, will keep the parts looking nice. JD

Michael Gilligan09/06/2017 16:03:10
16632 forum posts
724 photos


The best way that I have found is to use a GaryFlex block [which is rather like the old school 'ink rubbers'], with Solvol Autosol polish as 'lubricant'.

Yes, it's abrasive ... but very mildly so.


Involute Curve09/06/2017 17:33:22
337 forum posts
107 photos

I vapour blast all my crankcases as a matter of course, the finsih is as new, but you must make sure you clean all oilways etc afterwoods.


Neil Wyatt09/06/2017 20:14:13
18316 forum posts
718 photos
77 articles

I used my ultrasonic cleaning tank with a 'sensitive metals corrosion remover'. Not obvious from these shots, but it removed white 'bloom' as well.

before 2.jpg


Ian Skeldon 209/06/2017 23:36:17
489 forum posts
41 photos


and don't ask me how I know wink

ronan walsh10/06/2017 00:37:19
544 forum posts
32 photos

I boiled up some old cases in water with normal washing powder in it, the cases came out like new. But i tried it with a separate set of case sometime later, and they came out a blackish grey colour, not nice at all. Someone said it was because of the silicon content of the aluminium reacting with the contents of the powder.

thaiguzzi10/06/2017 06:26:58
698 forum posts
131 photos
Posted by Involute Curve on 09/06/2017 17:33:22:

I vapour blast all my crankcases as a matter of course, the finsih is as new, but you must make sure you clean all oilways etc afterwoods.


+1. Wot he said.

There is no better finish.

Tim Stevens10/06/2017 11:37:22
1271 forum posts

Ronan is correct - some Aluminium alloys contain a high proportion of silicon, and when the Al is eaten away (by eg washing soda, or worse, caustic soda) the Si is left as dirty smudges. This is a major reason why anodising does not give good results on such alloys.

Aluminium does not rust
It crumbles to a greyish dust
And most of all what you can see
Consists of Al two O three

Cheers, Tim

gerry madden10/06/2017 23:10:48
140 forum posts
55 photos

Well as usual some great info there. I didn't know about vapour blasting did some research and I'm impressed ! What's more there's a small business not far away from me that does it so I'll be visiting them next week. And by the looks of it, there's quite a few more bits and pieces they can do besides my crank cases.

Thanks all for your input.


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