Ep 17: Restoring anodised aluminium on your motorbike

Anodised aluminium looks great … until it all starts to go wrong. Anodising is a very standard protective treatment used on aluminium/alloy motorbike parts, but when corrosion sets in it’s difficult to deal with.

You can’t just polish it out like you would with bare aluminium, and you can’t touch it up either. You have a handful of choices: strip it back and resign yourself to perennial polishing duties; get it sandblasted and powdercoated; or paint over it.

I decided to strip the anodising and either restore a “brushed aluminium” finish protected with hard-wearing two-pack (2K) lacquer; or give it a coat of basecoat metallic paint, once again protected with 2K.

So, why didn’t I go for powdercoating? Well, I can’t powdercoat myself, so I’d be putting myself completely in the hands of someone else and paying them for a finish that ultimately I might not be happy with. Also, the colour choices are limited, and although powdercoating is hard-wearing it isn’t straightforward to touch up if you get stone chips or other damage.

And what about re-anodising? The problem you’ve got with the subframe I’m restoring is that there are cast aluminium bits welded to regular extruded aluminium, and they have been treated separately before being joined together. So anodising them as one component could give an unpredictable finish.

The first step is to get rid of the anodising, and the simplest way is to hit it with a caustic oven cleaner. Caustic soda reacts fairly aggressively with aluminium, and oven cleaner is a relatively mild form of caustic. Just strong enough to break down the coating and let you get at the metal underneath. You can buy pure caustic, but setting up a bath for a larger component means mixing up a lot of it and the reaction can run away with itself, permanently damaging your job.

After 10 minutes or so you can hose off the oven cleaner, let it dry and see the results, which will probably be quite disgusting. The surface, if anodised, will probably go a chalky white; if it’s bare aluminium it might even go black and give you the fright of your life.

After anodising, for this kind of box section construction the best way to strip off the formerly anodised layer turned out to be a flap wheel. Watch the video to find out about what it looks like and how to use it.

Without giving too much away: I went the repainting route. Have a look at the video and you’ll find out all about the method for stripping anodised aluminium, then applying etch primer, base coat and two-pack or “2k” lacquer. Safety warnings apply when using 2k – it is a hazardous material and you need to protect your lungs with the right breathing equipment.

– Waz

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11 thoughts on “Ep 17: Restoring anodised aluminium on your motorbike

  1. Hey boys, long time no see. You off on a big trip somewhere or running out of steam? I hope it’s the first one, ‘cos I *******g love your site 😉

  2. Greetings Scruffy. We will be back with more videos – we’ve just got some other projects to get squared away. How does something on brake bleeding sound?

  3. Nice one, Waz! I’ve had problems with bleed nipples, specially on bikes that get used thru the winter. They dump evil quantities of salt on the roads round here. Never had to try it with ABS – all my bikes are relics!

  4. Yes Jon, bleed nipples and calipers generally can get in a right old state where salted roads are involved especially where you’ve got unlike metals in play. I had to drill and tap one a while back, and also had to throw out a whole caliper because of a pad pin that had “become one” with the caliper body.

  5. nice site guys,,, Im in the process of fixing up my old nx650 dominator, I wanted to ask your advice, My spokes have a fair amount of surface rust, i have seen some people who have podercoated their spoked wheels complete, hub, rim, spokes without stripping it down. I was thinking of doing this on my domi, the spokes are all nice and tight, i know it might be a problem to tighten any loose spokes later on down the line, if it gets to that stage where the spokes are starting to loosen off, i would probably just rebuild the wheel at that point. anyway, check out my website, you might find it interesting, i have rebuilt a few bikes, 1975 gt250 ramair, cb900, dt175 enduro, lots of pics :-) all the best, and keep up the good work!!

  6. G’day fellas, great vid. just one recomendation about base coats, When applying the clear you should do it as soon as possible once the base coat has dried to touch, otherwise you are risking the clear not adhering properly. (Probably more critical on larger components such as body panels). The reason for this is that once the base has cured too much the clear does not react with it to form a chemical bond between them.
    Cheers

  7. Fred, you are of course completely correct about clear coat ASAP after base. Unfortunately I didn’t have time in this instance, but I’m applying that lesson in future.

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