Restoration - Clearcoat CroMo Frame

[AaronJ]

Hey gang,

Just picked up my new 93 Team Marin.

The first task is going to be to restore the frame.

Its CroMo with a clearcoat, however, the clearcoat is stuffed. So too are the decals and theres a few spots of surface rust.

I plan to keep it as is and get a clear powdercoat.

My question is how do I strip and prep the frame?

In the past I have sand/bead blasted and then powdercoated with colour. Sandblasting is pretty bloody rough and leaves a horrible finish on the frame, so I am wondering if bead blasting will be gentle enough?

Once I get it back to bare metal how to I take out the few stratches and marks prior to the clearcoat?

Any advise is greatly apreciated.

Cheers,
Aaron.

 

[Max P]

Is there such a thing as clear powdercoat?

:?

 

[kaiser]

Cro mo is a type of steel used for the tubes and not the finish on the surface, if its shiny it could be plated or possibly painted.

 

[cherrybomb]

Is there such a thing as clear powdercoat?

:?

Yup.


If it is indeed Cro-Mo then you should be able to strip the paint and then re polish and re coat with lacquer or powder.

The problem every frame maker had with this is that the 'metal' be it polished or plated has to be a mirror finish which means there is no key for the protective coating.......and so it then flakes off. :?

Bit of a quandary really.

 

[Err]

Wouldn't bead blasting look ok and leave a suitable key for the paint?

 

[AaronJ]

Is there such a thing as clear powdercoat?

As Cherry said, sure is. Can be had in a few different finishes such as flat and the powdercoat version of gloss and high gloss.

Cro mo is a type of steel used for the tubes and not the finish on the surface, if its shiny it could be plated or possibly painted.

I realise its not a finish! I use the turn CroMo to ensure every knew what TYPE of steel I was referring to.

The problem every frame maker had with this is that the 'metal' be it polished or plated has to be a mirror finish which means there is no key for the protective coating.......and so it then flakes off.

This is indeed where the quandary is. The metal has it been plated. Nor has it been polished to a ‘mirror’ finish, though there must have been some polishing. The best I could describe it is a very soft brushed finish. Under the existing clearcoat it not super shiny. It just looks like really nice clean natural steel. It looks good, which is why I’d like to retain the look.

I guess my question was more about what method to use for stripping it. I fear sand blasting will damage the metal surface too much, hence asking how you guys thought bead blasting might go.

If I use a stripper, I then need to work out how to clean up and re-polish/brush the frame. That's a question too... How?

Oh… I should have done this to start with, but there area few picks here: http://www.retrobike.co.uk/forum/viewtopic.php?t=32831

Aaron.

 

[cherrybomb]

Bead blasting should give you a nice satin finish, or alternatively you could try chemical stripper and then medium/fine wire wool to finish.

Personally I think I'd try the bead blasting approach; less work.

 

[rody]

My advise from a long backround in finishing bicycle frames is to avoid the clear coat over base metal.

This has been discussed ad nauseum, but the end result is that due to the fact that there is no chemical protectant, the base metal WILL develope rust beneath the clear coat in a matter of 1-2 years, leaving the frame with ugly spider rivlets.

Clear powder is even worse, as it acts like a plastic bag wrapped around the steel, where as the liquid clear can at least breath a bit.

If you must, the best option is to use a chemical dip which will strip the clear without mechanical aids and then use red Scotchbright pads pulled around the tube followed by green. This will give a smooth even brushed look. Wipe with Acetone using lint free gloves over nitrile and then off to the booth immediately.

cheers,

rody

 

[AaronJ]

Thanks Cherry and Rody.

I stripped the frame bare today (2kg on the nose, so not as light as I thought) and I think I'm just going to go a colour of choice and be done with the metal finish.

I found a small inward dent on the mid-outside of the left chainstay. Its not big (about 15mm diam and 2-3mm deep) but enough to annoy me. Does anyone know if the frame is bead blasted ready for powdercoating, can you fill the dent and then powdercoat over the fill? Or will the heat be a problem for whatever fill I use?

Cheers,

Aaron.

 

[Max P]

You can't PC over non-metallic filler can you?

Can you post some pics of the finish you have - be interested to see.