Let's Play (?) - Polishing Alloy Bonnet

[Zenki]

Figured this might get a bit lengthy so I decided to make a new thread. No, it's not a Subaru; the bonnet is off im-a-bus' NA Miata.

Just been stripped back to bare aluminium with a random combination of 120, 150 and 240 grit on an orbital. Didn't use paint stripper because a) the decent ones are fairly expensive, and b) I don't want to handle more harmful and/or caustic substances than I really have to.

It turns out that neither 3M 120 nor 150 grit doesn't stand up to aluminium very well. The box of 240 I have on hand (Wurth, I think) did a much better job of not being rendered useless in half a minute of sanding, so paint removal was mostly left to that stuff.

Now needs 500 with the orbital. The plan is to use some combination of wet sanding with 800, 1200, 1500, 2000 and 3000 grits. Haven't decided whether to finish with Mothers aluminium polish or 3M cutting compound and machine glaze - I've never worked with bare aluminium before, and apparently Autosol doesn't do a good job on aluminium.

Yes, those are dents, which I am extremely unhappy to see. I can't really do anything about them because I can't access them from behind, the interior structure of the bonnet is in the way. I'll probably have to perform some wizardry with vinyls and a Mazda emblem I salvaged from a second-hand Demio tailgate to cover them up.

im-a-bus wants to use a Z badge from her 300ZX instead. Nissan owners

Shouldn't be too hard to get rid of those machine marks, but we'll see how it goes. They're fairly fine.

Work stopped at this point because I like being able to use my wrists thank you very much.

Edited October 13, 2015 by Zenki

[hijacka]

Autosol does a great job on alloy like most polishable metals , I love autosol best polish you can buy and its one of the cheapest! Those scratches look deep. Problem with going through all those grades of sand paper is you will pickup grits and dirt as your rubbing and scratch it up again. if i wanted to be a ahole to other motorist and shine up me alloy hood so it blinds oncoming traffic i would strip it, go 800 wet then 1200 wet then slow da polish with autosol and wipe over with microfibre cloths . buff it then get some renaissance wax on there to slow down the oxidization process.. i use renaissance wax on polished rims and recently the brass and copper on 40year old marine engine parts, seems to work to a degree but you have to keep applying it

[Leufkax]

Autosol is the ****

[Zenki]

Work on this has been on and off, but here's a big progress update.

Wet sanding by hand to... I think it was 800 grit. The sandpaper does not last long at all against this aluminium, it definitely wasn't intended to be used on metal. I rather like the brushed effect this has, but it'd be too difficult to get a brushed finish consistent over the entire bonnet by hand.

Polished up a little test patch to make me feel better about all this work, got nice and shiny but machine marks are now blatantly obvious in the polished finish. F***K!

Back to square... not one, about square three. Took the entire thing back to 500 grit, then wet sanded with 1000, 1500, and 2000, that seems to have dealt with the machine marks for the most part. There's still a couple of swirls and scratches visible, but I'm not too fussed - this is going on a racecar anyway, and it's just a practice run since I intend to polish the bonnet on my MX-5 when I buy that.

Polishing this by hand takes forever...

Like, seriously...

On the plus side, something in these metal polishes kills mosquitoes.

Eventually got tired of rubbing at the entire thing by hand. Managed to pilfer the big ol' Rupes rotary buffer from work, bought a cheapo polishing pad (cheers to Firenza for delivery) and went at the bonnet with that and the Mothers alloy polish. Only took a couple of hours to finish off the rest of the bonnet:

I'm now on the hunt for an even finer polish and the softest cloths I can get my hands on to bring it right up to a mirror finish - as it is now, it's a little bit dull in spots. Might just need a bit more rubbing by hand while attached to the car, I've found it's difficult to get good pressure on the bonnet without it securely mounted at waist height or so. Maybe I'll give those 3M paint correction products a go. The cutting compound does seem to be aggressive enough to polish aluminium (telltale blackening of polish) so hopefully their Machine Polish and Ultrafine Machine Polish should be in the same basket.

There was a little discussion about the cost of doing this if someone pranged you, bent your bonnet, and had to pay to replace it. A fairly standard insurance rate is $52+GST/hr, and I'd estimate this would take 15 hours if done properly. Let's call it $120 for materials - paint stripper, sandpapers, polishes, polishing pad, tons of cloths and rags - and you're looking at well over a thousand dollars not including initial purchase of the bonnet. Ouch.

[boon]

I'd love to know whether this is legal on the road.

Even the scrutineers might throw a hissy fit about it. The potential to dazzle the crap out of another driver seems pretty high to me.

[Zenki]

Would depend on the car, I would imagine - MX-5 bonnets are fairly close to horizontal, there's no real way to get the sun reflecting off it into oncoming traffic without the sun blasting said oncoming traffic in the face anyway.

[Joker]

yea true but like Sticker number plates you'll likely get away with it in one of those cars