I’ve decided to utilize somehow my old Specialized Sirrus frame. The frame looked awful so needed to be repainted. And here starts whole story about painting alloy frame. If you ever tried painting aluminium, you know how tricky it is. To save your effort will be better to strip the frame from any hardware, and find company which will sand it down and powder coat it for you. You’ll wait 2-3 days, job done. Otherwise the job is painstaking, laborious, will take quite a long time, and you shouldn’t do it. 😉 I’ll try to describe below why.
Sometimes it’s not necessary to remove paintwork completely to the bare metal. If you’re lucky and haven’t got big chips of paint you can sand it down an paint it again. The fun begin if you have deep scratches, chips or rust/oxidisation underneath the original paint, and you need to remove whole paintwork. It’s laborious. Prepare yourself for at least 8h job. You’ll be sick after two hours so will probably take 2 days or so, to do it properly. (seriously, don’t do it! find company, pay for the job, and in the meantime drink beer, wine or even clean up cassette or degrease chain if you wish). Anyway, I found quite helpful using some tools like Stanley knife (you can scratch off the paint in some places), rotary wire brushes for drill at low speed as it’v very easy to go deep into aluminium (use googles! save your eyes you’ll need them later on), obviously sandpaper, orbital sander might me useful as well for tubes. Some areas will be hard to reach, but ultimately will be unlikely to chip or scratch the paint there, so don’t go crazy in places like seatstays-seatpost joint, chainstays-bottom bracket. (Anyway it’s not too late. Don’t do this, find a place which will do it for you)
Ok, so you decided to remove paint and you’ve done it. Enough? Not? (It’s still not too late go give it to someone which will paint the frame for you). Anyway, if you have naked frame at this point, and you still convinced to diy, you need to secure all threads and areas you don’t want to be painted. I’m talking about bottom bracket threads or push fit (depend which system you’ve got), bottle cages threads, v-brake threads (if there’s any), rack mounting threads (if there’s any), inside head tube, inside seat tube. For BB you can find cork from milk or something wrap with tape and push. same with headtube. If you’ll be painting by yourself you’ll probably place the frame upside down on some kind of pole inside seat tube, so won;t be a problem. For all threads you can use ordinary screws 4-5mm, v-brake pins might stay and should be covered with sealer tape.
Now you need to find a place, where is relatively free of dust and not too cold. Technically, you can paint the frame even when is around 5C (despite what is written on spray cans) but you’ll need add extra 12-24h, on top of recommended time, to dry out each layer. (it’s not too late to let do it someone else…)
Ok frame is on the stand and you still want to do it. At first of all needs to be degreased. Use alcohol and you’re ready to paint first layer which is in this case is etch primer. Etch primer will increase ability to sick next layer (which will be actual primer). Remember after each layer you must use fine graded coarse pad to slightly rub whole frame (equivalent of sand paper 500). That is to increase grip of the next paint layer layer. It’s actually quick process scratch slightly the whole frame is about 15-20 min and paint job is probably another 10m. The most painstaking thing is waiting, be patient! don’t rush! Did I tell you that will be long? 😉
Next layer is primer. If you can, go for epoxy primer as it’s very good stuff and coating is better than any other primer.
Ok third layer (remember sanding slightly each layer) is actual colour. I’m talking about third layer but you might find some imperfections when the frame will dry out so might be another layer or two of colour.
Finally when you’re happy with the colour it’s time to put some stickers now (or write something on the frame if you wish), obviously sand down slightly whole frame again and you ready for great finale!
Last layer is clear lacquer. Again if you are not happy with first layer apply another but remember to slightly sand the surface before.
Hint #1. If you painting by spray paint you need to remember that sprays are very thin. So effectively you’ll have very thin layer of paint (which sometimes is good, primers for example). Ultimately paint is not always covering properly previous layer (specially if primer has got different colour). The other bad thing is more likely you’ll have splatter. (I told you to give it to specialist, didn’t I?)
Hint #2. The other thing is sanding between layers. There’s couple of types of sanding pads used for sanding. If you’ll be painting with spray you have to use the finest one (equivalent of 500 sandpaper). If you have access to paint gun and compressor, you can use more coarse pad. With paint gun layers might be thicker and it means will cover imperfections better (specially lacquer on top and primer)
If you’re happy with you paint job let another 48h to dry out completely. Normally I’m sleeping in bed with my freshly painted frames first two night’s (Droit du seigneur – or “right of the lord” if you like), so they are fully domesticated afterwards and should know “who’s the master”. Obviously you can be harsh and leave them in garage or shed ;-).
Conclusions. I’ve spent £24 for sprays and left with half can of a etch primer (you not using it too much just a very thin layer) and less than a half can of lacquer. So lets say I’ve spent 20 odd quid for materials. You can think it’s not too bad, but in terms of labour it’s completely different story. Removing whole paint took me 2 days lets say 2x3h, and painting 5x1h five visits over whole week. started on Friday afternoon and next Friday I had painted frame, still not ready for assembly as lacquer looked very fragile at that point. Effectively I’ve started assembling Monday afternoon. In the meantime I’ve figured out a business near me which will powder coat frame in a week or so for £70. Pop in on Monday leave frame, collect on Friday and ride Saturday. Looks like better plan for me. Powder coating is stronger and the frame is usable straight from a oven. Think about that before start.