Painting a bike frame


Paint protects steel or aluminium bike frames from water and grit that would otherwise cause corrosion. So it can keep doing this, it needs repairing when it gets damaged. If there’s rust, that will need removing and the metal will need to be treated to give the new paint something to stick to.

This page shows the materials, products and paints I’ve used at home for these jobs. The process is the same for an entire frame or a single tube. My experience has been entirely with steel frames, although the notes on paint brands will also apply to alu frames treated with etch primer.

Here’s a bullet-point summary of the information in this article.

  • DIY paint is relatively soft and each coat you apply will take a long time to cure. A paint job requiring multiple coats can take weeks.
  • Components must be removed. This makes the prep easier and protects the components.
  • It’s worth using the best quality abrasives. This means aluminium oxide paper.
  • There’s usually more rust under the paint than above. It needs removing as far as possible. Deep rust needs treating.
  • New paint will not adhere to bare metal or unprepared paintwork.
  • Metal needs degreasing and priming. Existing paintwork needs scuffing and degreasing.
  • Using rubber gloves when handling the frame means you won’t need to degrease it a second time.
  • Your choice of colour can affect how many coats you need. Lightening a frame takes more paint than darkening; repainting in the same colour takes less still.
  • Paints differ in viscosity, opacity, cure time and hardness, and not all paints are compatible.
  • There are pros and cons of spraypaint versus brush paint. Your choice may depend on how large an area needs coating.
  • Sanding between coats helps give a smooth finish.

Reasonable expectations of a DIY paint job

Here are two points to bear in mind if you’re considering painting your own bike.

  1. A factory-quality paint finish is near impossible to achieve at home. Professional paintshops in factories use two-part paints with chemical hardeners, or electrically charged powder, and curing ovens. DIY paint won’t be as hard and will need retouching after a little while. You can mitigate this by leaving each coat to cure for an extended period of time. However this means…
  2. Doing a paint job at home takes time. The prep takes hours and curing can take weeks. You’ll need a spare bike to ride while your bike is being painted.

If you need the frame finished quickly, or you don’t have a spare bike to ride, consider taking the job to a professional paintshop for bead blasting followed by powder coating or enamelling. If you’re prepared to wait a few weeks before rebuilding your newly painted bike, and you’re willing to retouch your paintwork after that, the info here will help you get acceptable results, which should be far better than you’d get with a tin of Hammerite. (More on Hammerite later.)

To date, I’ve repainted six frames at home, two with brush paint, four with spraycans. I learnt something each time. Here’s an explanation of the method I now use and the reasons why.

Prior to sanding

I always strip the components off the frame, even if I’m painting a single tube, because sanding dust gets everywhere and I don’t want it in the bearings or chain. Stripping and rebuilding a bike is time-consuming, so I hold off paint repairs until I’ve stripped the frame to overhaul the bike anyway.

If I need to sand the head tube, I remove the headset and head badge, because they’re difficult to mask. I once masked a Raleigh heron badge in situ, but it was fiddly and wasn’t worth the effort. A head badge can be replaced later, but I usually leave it off because this makes it easier to use a frame pannier on the bike.

I thoroughly clean the frame with mild detergent and warm water to remove dirt. Next I wipe it down with white spirit to remove any oil or grease. I pay particular attention to the drop outs, the areas around the brakes and the fork crown – dirt here can be stubborn. I degrease even the parts that won’t be painted, because dirt has a habit of spreading when handling a frame and I don’t want any dirt on the surface to be painted.

If there’s any sign of rust under a decal, I remove the decal. Decals come off better when they’re warm, as this softens the glue. I use an electric heat gun on cool setting. The curved edge of a shave hook is good for getting the decal off in one piece. A denim rag soaked in white spirit removes the residual decal adhesive.

Flaking paint elsewhere on the frame can be removed with a pen knife or the corner of a wallpaper scraper. I use protective goggles to protect myself from flying paint flakes.

Rust patterns on steel bike frames

Rust spots that have broken through the top coat of paint are evidence of a larger rust patch beneath the paint. The worst case I’ve seen is a 1cm rust spot on a down tube which was a 15cm stripe when I got to the steel.

I’ve also seen ‘wiggly worms’ or ‘veins’ of rust on their own, which have raised the surface of the paint but haven’t corroded the rest of the steel. They weren’t particularly deep (a fraction of a millimetre) and on the frame in question, which had thick, high tensile steel tubing, I was able to rub them away completely without weakening the tubing.

If a bike has been ridden without mudguards, the underside of the down tube and the bottom bracket shell is usually worse than the rest of the frame.

Rust removal techniques

Standard sandpaper wears out too fast when rubbing down rust but aluminium oxide will do it. Wet and dry paper is better – it’s black. Aluminium oxide paper – green – tends not to clog up with dust and lasts a very long time. I bought a pack in 2003 and I’m still using some of it thirteen years later. Non-clogging papers are best for this kind of job as you can clear the dust simply by flicking the back of the paper.

If the frame is very rusty, I start removing it with 80 grit paper. Thin-walled steel tubing (Reynolds 531 etc) can be damaged at this grit, so I press lightly and change to a finer grit as soon as I’m through the corrosion.

A miniature orbital sander, or mouse sander, can be used at the start of the job and can be a good way of reaching hard-to-reach places such as lugs, joints between tubes and bottom brackets. Take extra care not to go too deep; an orbital removes material in seconds. The abrasive papers for mouse sanders are relatively coarse so I’ve fitted the finest ones available, finishing the area by hand.

Rust spots often have wiggly ‘veins’ of rust around them, where the rust is creeping out to colonise a larger area of steel. When I see these, I know I’m reaching the edge of a rust patch. I select a grit that will remove as little good steel as possible and finish the rust removal stage with 320 grit.

Where rust veins appear without a central rust spot, I use coarse (80 grit) paper just to remove the paint and then rub the rust out with 240 or 320 grit and then wire wool. I then dust the whole frame with a dry paintbrush to remove any wire wool specks. (These specks oxidise quickly and can stain the paint.)

Plain sections of tubing can be sanded by hand with a strip of paper held at each end and pulled side to side, using a shoe shine action. This removes material relatively quickly, so keep checking the surface.

Degreasing the frame immediately prior to painting

I degrease the frame with white spirit on a lint-free cotton cloth to remove any oils. After this stage, I wear rubber gloves.

I degrease the frame an hour before I am ready to apply the first product (i.e. the primer). An hour is long enough for excess white spirit to evaporate from the surface. I degrease the frame in the place where it will be painted.

A frame can be hung beneath a washing line, with a string through the head tube. The string is clipped to the washing line with a carabiner. The frame can then be rotated for painting and left hanging while the paint dries. It can then be moved on its string by unclipping the carabiner from the washing line.

Steel treatment – rust converter or anti-corrosion primer

Kurust is a water-based rust converter product made by Hammerite. I’ve used it to deal with small amounts of rust in scratches beneath the surface of the steel, when I’ve decided not to sand any further into a thin-walled tube, after removing the rest of the rust patch. You brush it on with a fine paintbrush and a few drops go a long way. Kurust comes in a small white plastic bottle with a yellow label. I bought some in Halfords for a little less than £10. The Kurust acts a primer and can be top coated as it is. The Kurust dries in minutes to a blue-black colour. I’ve had it dry brown once, when I guess there was some rust I hadn’t removed, so I sanded it again and recoated, and it went blue-black like it’s meant to.

Anti-corrosion primer gives the paint something to stick to and helps prevent rust if the top coat is subsequently chipped. I have used it when there’s absolutely no rust left and the steel surface is silver coloured and smooth. It comes in an aerosol can. I’ve used Isopon Zinc 182 brand, which cost £10 from Halfords. It’s mid-grey in colour and can be sanded after a few days, though it’s soft and slightly tacky before that. I’ve seen David’s anti-corrosion primer with the same branding (yellow and black tin).

Primer stinks and gives me a headache if I inhale the fumes. What’s more, it stinks for a number of hours after it’s been applied. So I use it outside.

Primer is gluey when wet, so I clean the spray nozzle immediately to prevent clogging and splattering next time.

Colour choice

I try to avoid changing the colour of the paintwork, because it takes more coats. Some brands of paint can be colour-mixed to achieve a match. It usually says on the pot if the paint is mixable. If I’m mixing a colour, I do it in daylight, rather than artificial light indoors, to be sure it is an accurate match.

When I have tried a colour change, I’ve found darkening easier than lightening. White paint over anything else will take multiple coats to get to pure bright white. I’ve done up to six thin coats of white on a frame – and I wouldn’t bother painting white on a bike again. Black is a good choice for a bike frame, as it can be retouched/maintained easily and black paint will be always easy to find – there’s only one shade to choose from!

Paint application: spraying (recommended)

Spraying allows you to lay down a thin, even coat of paint surface quickly, even in hard-to reach places. Because spraypaint coats are thin, spraying allows the application of successive coats more rapidly than brush painting allows. Spraypainting is a craft in itself and it takes practice to get an even finish with no runs.

Bottom bracket shell covered with an old BB cup and taped over

Bottom bracket shell covered with an old BB cup and taped over

Mudguard eye filled with a bolt and derailleur hanger covered with a nut, bolt and washers

Mudguard eye filled with a bolt and derailleur hanger covered with a nut, bolt and washers

Spraying requires the filling or masking of threads (bottle bosses, brake posts, derailleur hanger hole, bottom bracket, pannier braze-ons, mudguard eyelets).

Spraying should be done in a controlled environment (ideally no wind, no dust that can be kicked up as you move around, and no flying insects).

Shake the can for at least two minutes so the internal ball thoroughly disperses the pigment. The paint may not be at full opacity for the first few seconds, so test it on a piece of card. Hold the can 10″ or further from the surface and keep moving it. If the paint drips, it means one of three things:

  • I’m spraying an area that already has wet paint on it,
  • I’m moving the can too slowly along the surface, or
  • the can is too close to the frame.

Most spraypaint is formulated to be built up in multiple thin coats. I remind myself that if it feels like I’m not putting on enough paint, I’m probably getting it right. It’s easy to accidentally over-spray a tube you’ve just sprayed near a frame joint. Areas particularly at risk of overspray are the joints at the bottom bracket and the seat cluster. I’ve found that doing this entire area in one go gets too much paint on the seat tube, because the seat tube gets hit from multiple angles. The excess then sags and has to be rubbed down. To avoid this build up of wet paint, I’ll sprayed one side of each tube during the first session, and the other side during a further session, so that any overspray hits only dry paint.

Paint application: brushing

When paint is applied by brush, it needs sanding prior to the final coat, and perhaps between coats, depending on the formulation of the paint. This is doable on the plain sections of tubing, but can be tricky at lugs and around bosses. Brush paint takes longer to cure (each coat can take a number of weeks), because it goes on thick. Thin coats cure faster but of course you need more of them. A paint that is formulated to leave no brush marks can look great.

I’ve tried brush painting an entire frame but it was fiddly getting into joints, and even more difficult to then sand those areas smooth if I applied too thick a coat. But brushing can be the quickest way of painting small complex areas with multiple faces, such as cable stops.

Brush painting doesn’t need a special environment, just a ventilated room, nor does it need extensive masking of the frame because there’s no ‘overspray’. For these reasons, brush painting ideal for small touch-up paint jobs.

A minute or two after I’ve finished a brush coat, I check for drips that have begun to form. To remove them, I dip the brush in thinner, dab it on a cloth, then touch the drip with the brush tip. The brush then soaks up the dripping paint by capillary action.

Sanding between coats

When brush painting, I sand between coats with 800 grit paper, to remove brush marks. In the past I’ve not bothered rubbing down, assuming that the next coat would fill the low points in the previous coat, but this doesn’t work, particularly if the new coat is thicker than the last as the thicker paint doesn’t reach the low points, with the result that brush marks end up exaggerated rather than diminished. If I’ve just done a thick coat, I’ll leave the frame hanging for a fortnight or more, to make sure the paint is hard enough to sand without it crumbling. Paint drips don’t harden as they’re so thick, so I cut them off with a scalpel. When the remaining paint has cured, I rub it down, dust the frame with a clean paintbrush and apply a final coat.

After painting

A DIY paint job will take weeks to cure. I hang the frame on the wall for a month before fitting components. Even then, it’s not as hard as factory paint. I tape the area beneath a front derailleur band using electrical tape in a matching colour so the clamp doesn’t bite into the paint. If I’m attaching a rack with p-clips, I’ll also tape the seat stays for protection from those clips.

A DIY paint job will need retouching more often than factory paint, so I try to save a bit of paint for that purpose.

Storing paint for touch up

It might be a number of years before you need to retouch your paint, in which time you might have forgotten which brand of paint you used, or the manufacturer might have stopped making it! A small amount of paint can be stored in a small jam jar. Fill the jar to exclude air and store it upside down so the paint seals the lid and label it.

Aerosol cans depressurise over time but should be okay for a year or two. They must be stored away from direct sunlight. It’s good to store paint products and thinners in an airtight cupboard. A disused refrigerator is ideal.

Paint reviews: brush paints

Plasticote Enamel, oil-based
Brushed on Plasticote enamel leaves no brush marks and leaves a relatively hard gloss finish. It is quick drying and cannot be worked after five minutes, so you need to mop up any drips as you’re going along. Unthinned, it seems to cure to a level where it can be sanded after two weeks. Sanding during week one causes small ‘crumbs’ of paint to break away from the surface, and in week two the paint hangs onto fine particles of grit or dirt introduced by the sandpaper. In week three these problems are gone. Light colours don’t have particularly good opacity, so a matching base coat is needed. I bought my Plasticote in 2006 when it was made as an oil-based paint and sold in glass jars with steel lids – it’s this formulation that the above review is based on. In 2016, there’s a product with the same branding being sold in plastic containers as a water-based paint, but I haven’t tried this, and I doubt that any water-based paint would have the necessary hardness and adhesion for use on a bike frame.

Humbrol enamel, oil-based
Brushed on Humbrol takes weeks to cure and can react with subsequent coat of oil-based paint, including additional coats of Humbrol: the brushing action drags the previous coat(s), leaving you with a lumpy surface. That’s why the tin says it’s best applied in a single coat. It has good opacity.

Johnstone’s Professional Undercoat
Johnstone’s professional white oil-based undercoat has been a good base for white top coat on plain tubing in locations where it can be sanded smooth. Unsanded it leaves brush marks. It’s a high build paint, so I keep it thin, especially in areas where components need to clamp to the tubing.

Household gloss paint
I’ve used Johnstone’s professional black gloss oil-based paint for painting tubing. Thinned with white spirit (six parts paint to one part thinner), it flowed into all the scratches and paint chips on the bike frame, although it became very runny. It was still soft enough to be dented by a finger nail during week two, but it hardened off during week three. It cured hard enough to sand between three and four weeks. Opacity is poor when thinned, so the tubing needed two to three coats.

At the same time, I painted some frame tubing and a handlebar with the unthinned paint. It was visibly thicker and after four weeks (1 May 2016) was soft enough to feel a bit grabby when I ran my fingernail along the tube.

UPDATE (6 June 2016): The thick coat took ten weeks to cure using ‘the fingernail test’. The coat on the handlebar that I brushed more to reduce the thickness cured in six weeks.

I’ve found that the Johnstone’s professional is not suitable for over-painting with Halfords oil-based spraypaint – the Johnstone’s base coat crinkled when oversprayed and I had to sand it down and do it again. I found that if I sprayed half a dozen dust coats, instead of one solid one, the crinkling was avoided, but took longer than sading off the Johnstone’s.

I’ve previously tried general purpose solvent-based gloss paint (Wickes own brand in white) on a top tube, but it didn’t cure hard enough to be properly scratch resistant and dirt became embedded in the surface.

I once brush-painted a Raleigh shopper frame and fork with pale blue Hammerite Direct To Rust paint as a base coat. The factory paint was metallic blue so I planned to replicate this with Japlac metallic blue lacquer over the top of the Hammerite. The Hammerite was horrible to work with because of its viscosity; it was like painting with glue, and I found it very difficult to achieve an even surface. A day or two later, I began top coating with the Japlac which dissolved the Hammerite so that my paintbrush dragged it around. That’s how I learnt the importance of waiting a long time between coats, although Hammerite takes longer to cure than most paints due to its thickness. I did that paint job in 2006 and I still have the paint stirrer I used for that job, and the paint on it is still soft – i.e. the paint hasn’t cured, even after ten years! I now avoid using Hammerite (and other paints described as ‘paint and primer in one’). I have seen that distinctive shade of blue on a couple of bikes in town and noticed that the finish was uneven and soft, which seems to confirm my theory that it never cures.

Water based varnish
I have used water-based varnish as a barrier coat between coats of Plasticote enamel on a replacement fork, to stop brush drag on a second coat the next day. The paint job proved plenty tough enough, if a little streaky due to brush marks in the water-based product. Nowadays, I would just leave the fork for a fortnight between coats.

Paint brands: spraypaints

Halfords acrylic spraypaint
I tested Halfords ‘appliance white’, over-spraying a white steel frame which had rust spots removed, treated and primed.

A very light coat dried with the texture of eggshell. Applying slightly more paint in a single session gave a smooth gloss finish. After two weeks hanging in a garage at an average of 12 degrees C, the gloss surface could be sanded with 800 grit in order to remove thick patches, captive dust particles and other imperfections. Where the paint was so thick it had sagged, the paint was still soft at two weeks (7 May 2016) and sanding at this stage produced surface craters where chunks of uncured paint had been pulled away by the sandpaper. I estimate four weeks cure time for sags and runs.

The instructions on the can say wait two weeks before smoothing the top coat with rubbing compound and 2000 grit paper, which seems to confirm these findings i.e. two week to cure for normal thickness. (2000 grit – now that’s fine sandpaper. I didn’t even know they made sandpaper that fine.)

One 500ml can of black paint covers two framesets when the paint is applied thinly. Black has very good opacity. White is less opaque and full coverage requires numerous coats. I’m up to four coats on a grey-primed frame and it needs a fifth for a solid colour (15 May 2016).

Halfords acrylic spraypaint can be sprayed on top of oil-based Plasticote enamel after the Plasticote has cured to give an inert surface. I sprayed Halfords white on Plasticote white after four days and it didn’t react.

Halfords acrylic spraypaint can’t be painted on top of Johnstone’s professional gloss from a tin. It may also be unsuitable for spraying onto other general purpose oil-based paints. I sprayed Halfords black on Johnstone’s black after the Johnstone’s had had four weeks to cure and the basecoat crinkled where the spray went on thick. Successive dust coats avoided the problem on another frame tube similarly painted, perhaps because the spray dried before the base coat had time to react. The other way round works fine: the Johnstone’s brush paint goes on top of the Halfords spraypaint with no reaction.