[Closed] What’s the paint stripper (or method) of choice currently?

Talk to your powder coater. It's not that common to blast paint off small items. They usually dip. If it was blasted at the time it was first painted then there might already be a profile too.

But if you want to strip then most will be the same performance wise. IT won't matter too much anyway because bike paints aren't particularly tough.

DIY paint strippers are hopeless, just don't bother, nitromors actually slows the process down as once the paints is slightly soft it just gums up the sandpaper, imagine trying to sandpaper toffee.

Take it somewhere and get it dipped/blasted. They might have something softer than shot or grit to remove the paint. Just be aware that the softer the media the more will be needed and the less it can be re-used so the price goes up.

If you have a compressor, you could have a look on YouTube and make a DIY blaster and use walnut shell.

I've done quite a few steel frames and run a few of them raw.

Firstly the paint stripper needs to have methylene chloride in it (old school nitromors) for it to work. You can still get mecl2 based strippers from eBay - but be warned it is classed as carcinogenic. The molecular size of mecl2 is small and will pass through standard activated charcoal filters - you need specific mecl2 cartridges.

Secondly - you will probably lose the weld heat colouration when you strip the frame depending on what the current coating is as even Mecl2 strippers will need a helping hand with a scraper/brass brush/scotchbrite pad which rubs off the colouration.

I might be wrong but I doubt any of the nice purpling around the welds will be left whichever way you strip the paint.

I’d just go to a powdercoating company and get them to dip the frame. Shouldn’t be that expensive and will save you a lot of mess / work.

Thanks all. Will give my local powder coater a buzz tomorrow.

Should he treat the frame with any anti-corrosion stuff before powder coating? Any tips or best practice?

Onzadog
Member
If you have a compressor, you could have a look on YouTube and make a DIY blaster and use walnut shell

Don’t tempt me....I do have a compressor and love a good project!

'

Should he treat the frame with any anti-corrosion stuff before powder coating? Any tips or best practice?

Probably, but powdercoat is bloody tough compared to paint, I wouldn't worry about it either way. I had a couple of frames done and neither picked up more than the odd chip that made it through to bare metal.

If you are clear powder coating then you can’t apply a corrosion inhibitor under the main coat. Clear PC coat over a steel frame can result in 'brown spiders legs' spreading out under the coating - just to be aware of.

Do not get the frame shot/media blasted - commercial powder coaters are too aggressive when it comes to blasting as they want quick turnaround.

Sand it for a rough finish and the let it rust a bit. Will take ages but isn't blasting.

(I've never heard of a painter dip a bike frame.)

Unless you have some sort of perfection in mind(which I expect you do)

Do not get the frame shot/media blasted – commercial powder coaters are too aggressive when it comes to blasting as they want quick turnaround.

Is that why all our frames fall apart after powder coating?

(Hint: they haven't)

I believe the baking/curing of the paint is the main concern - in aluminium bikes which can mess with the properties of the metal (Ali) after it originally being heat treated for strength. You have steel obvs so I’d be less worried.

I went for a soda/water blast on my last frame which turned out awesome and didn’t take any surface material away - no scratches or texturing.

No, don't pretreat the frame. Powder coating heats to about 200C so you want it to be as clean as possible. If you were paranoid then you could spray the inside after coating. The coating itself will do a reasonable job of protection while intact.

As above a clear coat will show some corrosion underneath. It won't be entirely impermeable to moisture. It may also yellow slightly. But long time scales. By the time it becomes a problem you'll be ready for a repaint or the bike will be obsolete.

Powder coaters are used to blasting smaller items. Mine does a good trade in alloy wheels. A commercial blaster will have the pressure dialled up and use iron slag grit. Last time I used a commercial blast setup it nearly lifted me off the floor at 70kg not including PPE! (NACE cip) But if you use a softer grit or a grit/shot mic at a lower pressure it'll be fine. Specialist places use all sorts. Dry ice, walnut, sponge etc.

Painters dip things all the time. Again my powder coated does spay work as well. Mostly conventional pot gun and airless air assisted work as they aren't into the large scale stuff where airless would be used.

Tips. Ask them what they do for prep. Mine does everything. They don't trust the customer. Prep is everything. Glean and degreasing is vital. They will also mask as they have all the right materials. Ask them if they do bike frames regularly as if they don't they might miss some of the smaller threads for mud guards. You may need to chase some of the threads in any case before reassembly. I managed the BB with a scalpel and guards with a steal bolt and patience.

If your frame is faced now you should get away with just cleaning the faces after painting. Again a scalpel worked.

Walnut shell blasting probably won't be aggressive enough. I took an old Raleigh Team Panasonic 753 frame into work, to blast it in the "small car sized" blasting cabinet. This is before and after

I had to use the similar sized shot blaster to remove all the paint, before I could repaint it

Going back to paint stripper. We use this Starchem stripper. It takes powder coating off nicely and other coatings too although it is quite strong it’s not in the same class as some industrial ones that can eat flesh away! ( I’ve seen it happen!!). Usual precautions apply, use goggles, gloves and don’t drink it etc.

https://groveshop.co.uk/other-consumables/19945-starchem-synstryp-paint-stripper-5-litres-sps5.html?gclid=EAIaIQobChMI1v_mwcKf6AIVh6ztCh0psQnqEAUYASABEgKFvvD_BwE

Thanks all.
Looked at getting the paint baked off but decided to go DIY as first effort.

Thanks teamslug. That starchem stuff looks promising. Will investigate the further.

Any other paint stripper recommendations that aren’t quite as large volume?

Many years ago I had a steel frame blasted by my LBS they did it in house and must have used something fairly fine/soft judging by the fine patina it left.