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Retouching frame finish

Posted: 31 Aug 2019, 8:08pm
by Junglist
I have damaged the finish on my frame by using an ill-fitting BB tool. There are 3 areas on the bottom bracket shell, 2 underneath and 1 on top. The finish is a textured matt black anodising on a 7005 T6 alloy frame. I have rubbed down the areas ready for painting as shown in the photos.

Image

Image

My research has suggested I need an etching primer, although I don’t know what effect it may have on the surrounding anodising. I had hoped to use a brush rather than spray but this I understand is not advised as you need a thin layer which is difficult to control with a brush.

As for the top coat, I’m not sure if matte or satin will be the better match and there’s so many different types of paint I don’t know where to start. I’m not expecting a professional finish, just a hard wearing one.

I also need advice on masking tape as I don’t want paint on the face of the BB shell.

Thanks, Mark

Re: Retouching frame finish

Posted: 1 Sep 2019, 8:54am
by David9694
So what we’re seeing in pics 1 and 2 is a ring of bare metal on the underside; where have you got to in 3? In 1 and 2 the cleaned area looks slightly raised, or is that a trick of the light?

https://www.duplicolor.com/product/text ... ive-paint/

You’ll know that conventional car and bike finishing is all about a smooth consistent finish. There are textured paints, like the one above, but I can only think it’s trial and error to get a paint that matches your particular black and is close to the particular texture of the anodised finish. It depends on how much trouble/expense you want to go to : A specialist supplier might be able to advise and mix something. The standard nozzle is for covering large flat areas - maybe there’s something finer for your situation?

I thought the silver bands looked quite good. Depending on the colour of your b/b, one option would be to have a contrast band that picks up another colour on the bike?

Re: Retouching frame finish

Posted: 1 Sep 2019, 9:06am
by the snail
You can buy primer for aluminium/non-ferrous metals, to apply with brush (hammerite/rustoleum?) from somewhere like Halfords or B&Q. I wouldn't want to use a spray can for such a small/awkward job.

Re: Retouching frame finish

Posted: 1 Sep 2019, 6:19pm
by ian peacock
For a small area, nail varnish works well. you can take your frame into the shop and get an exact (ish) match.

Re: Retouching frame finish

Posted: 1 Sep 2019, 9:41pm
by AndyA
I reckon that frame is either anodised or cerakoted. *edit-noticed you said it was anodised* Not that it really matters for your purposes, you can't use either process to touch up, so you'd be using paint regardless.
If I was you I'd use spray.bike, the rough matt finish that stuff gives is very similar to the frame and it's as tough as anything that comes out of a can. No overcoating required.
The best masking tape I've used is Frog delicate (yellow). If you get the 50mm wide roll you won't need to join bits to cover the entire BB face.
You'll get a bit of overspray on the frame, some would mask everything from the BB welds up, others wouldn't bother. I wouldn't bother unless you've got some contrasting panels or decals in the line of fire

Re: Retouching frame finish

Posted: 1 Sep 2019, 10:27pm
by fastpedaller
I'd use a fine brush for that.

Re: Retouching frame finish

Posted: 1 Sep 2019, 10:37pm
by PH
You've done a neat job of rubbing it down, I'd show that off with a bit of clear lacquer, no one will know it isn't meant to be like that.

Re: Retouching frame finish

Posted: 2 Sep 2019, 1:23pm
by Junglist
Thanks for all the replies. :)

David9694 wrote:So what we’re seeing in pics 1 and 2 is a ring of bare metal on the underside; where have you got to in 3? In 1 and 2 the cleaned area looks slightly raised, or is that a trick of the light?

“1” is a patch of bare alloy 35mm by 6mm, “2” is a patch 50mm by 6mm. The areas are slightly raised from the centre of the BB shell.
“3” is an area with indentations. I didn’t rub that bit down but I think I probably should even though I won’t get a completely flat surface.
David9694 wrote:I thought the silver bands looked quite good. Depending on the colour of your b/b, one option would be to have a contrast band that picks up another colour on the bike?

I hadn’t thought of spraying the area all the way around in a ring on both sides, but it could work. The only other colours on the bike are gloss black decals, so potentially I could spray in gloss black.
AndyA wrote:If I was you I'd use spray.bike, the rough matt finish that stuff gives is very similar to the frame and it's as tough as anything that comes out of a can. No overcoating required.

That's good to know. I had seen this paint and wasn't sure how it compared to car paints.
AndyA wrote:The best masking tape I've used is Frog delicate (yellow)

Thanks.

Re: Retouching frame finish

Posted: 2 Sep 2019, 1:55pm
by Brucey
the other thing you could do is not to fuss with it; any paint you can buy won't stick as well to aluminium as what was originally applied and it probably won't match anyway. To cover up the damaged areas I'd suggest using tape. Insulation tape is stretchy enough that you could wind it over the BB shell even though it has a step in it?

FWIW it looks like a textured paint finish rather than anodising.

cheers

Re: Retouching frame finish

Posted: 2 Sep 2019, 10:03pm
by David9694
I had a feeling this was a Stealth bike!

I tried Spray.bike, but I found it didn’t live up to the hype. Sent that frame be be powder coated.

If Brucey’s assessment is right, a complete powder coat finish while drastic, might be another option.

Re: Retouching frame finish

Posted: 2 Sep 2019, 10:32pm
by Junglist
Thanks, I'll add tape to my list of options.

Apart from powder coating I suppose car paint is the next toughest paint?