Paint vs Powder
Ok, so you're restoring your dream bike and inevitably, you will come to a fork in the road - the same fork every restorer comes to (pardon the pun). Which paint? Or is powder-coating best? What about rattle cans - are they any good? And how about painting my engine, callipers, hubs, exhaust and muffler - do I need a special heat resistant paint? The short answer is it depends on your budget, DIY skillset and the particulars of the item you want to paint.
SURFACE PREPARATION
Preparing your substrate is a critical first step in ensuring that your chosen coating system will perform at its best, no matter whether you choose paint or powder.
Do I need to remove the old coating first? Yes. There is no telling the quality of the existing paint - best to remove it.
Media blasting is recommended if you need to remove an existing coating. By doing this, you can remove the old coating and prepare the substrate ready for it's new coating in one fowl swoop.
Contrary to popular belief however, you do not need to blast all surfaces prior to painting, they can simply be cleaned using white spirits (mineral turpentine) or methylated spirits. Both are solvents (petroleum and alcohol based respectively), and both will evaporate quickly after use. Primer (next step) can be applied directly to an un-blasted surface.
Is there an exception to the rule? Yes. Media blasting is recommended for substrates that will receive powder. This helps the powder adhere to the metal. Similarly, for painted surfaces, even though you can use an etch primer, the roughened surface further assists adhesion and therefore durability.
Pro tip: Avoid handling a blasted or cleaned surface with you bare hands. Your hands have natural oils that you do not want on your surface.
PRIMING
No matter whether you are painting or powder-coating your item, the surface can still be primed. The powder system uses a polymer-based primer that is both compatible with the top coat and being applied electrostatically. Painting meanwhile has the option of epoxy or etch primers. Which one you use will depend on the condition of the receiving surface prior painting.
Epoxy Primer: Epoxy primers are generally used on large metal surfaces (e.g. car panels). This fully protects the surface from the elements, meaning you can work at your own pace without worrying about rust forming. You can also apply body filler directly on top of sanded epoxy primer, giving you the option of re-visiting your bodywork as you go by simply applying body filler on top, and then re-spraying epoxy to the area. This makes epoxy primer a more logical choice for jobs that require major bodywork that you might need to revisit more than once. The downside of relying on epoxy adhesion is you have to manually create the bite needed for epoxy primer to successfully attach to the metal, which can be done by sanding or blasting. Epoxy primer also takes longer to finally cure.
Etch Primer: Wherever possible, this is the preferred primer. Why? It uses a chemical bonding system comprising phosphoric acid and zinc chemicals to promote adhesion whereas an epoxy primer relies on only mechanical adhesion via a roughened surface. Etch primer has best durability but cannot be applied over filler repairs.
POWDER-COAT
To understand powder-coating and its performance relative to paint, you need to understand how it is applied to the metal. Powder is electrostatically applied. That is, electricity is used to attract and bond it to the metal. It is a great solution for coating items that have difficult to reach or complex surfaces such as coil springs, rocker covers.
The downsides? Well, powder just plain isn't as durable as paint. Additionally, colour options are limited for powder. Paint has infinite colour options and colours can be mixed. Painting offers more customizability such as being able to tape off sections that you don't want coated or leaving sections for polishing such as on alloy wheel rims.
2K PAINT SYSTEM
What is it? Simply put, it is a two-component paint system in which a chemical reaction results in paint hardening. Hardeners combine with the base paint to form a very durable coating. The 2K system is used in the top coat (normally the final clear-coat). 2K systems (as opposed to a 1K system) is preferred by spray painters as it provides awesome durability with little extra work.
A typical 2K paint system might look like this:
- Etch primer, 1.5 coats (1 coat plus a touch-up)
- Base coat (colour), 2 coats
- Clear coat (2K). 2 coats is standard, 3 coats for a super-good finish.
Pro tip: Always filter your paints when mixing.
Here at OEM, we generally use an acrylic-urethane clear-coat paint for most of our work.
What is acrylic-urethane? Acrylic-urethane is the most commonly used commercial automotive paint. It is a water-based gloss coating and offers outstanding abrasion resistance and has excellent wearing properties.
Is there an alternative? Yes. Polyurethane. It has excellent comprehensive performance such as a thick coating, fairly smooth surface and outstanding chipping resistance. It is more commonly used in industrial applications for rust prevention and applications requiring superior durability. It's finish is not as good as acrylic.
RATTLE CANS AND HEAT RESISTANT PAINT
Ok, so we always suspected that rattle cans were a little but dodgy. And after reading the above, you can draw your own conclusions.
At OEM, we would never used a rattle can on any of our products or restoration projects. For efficiency and cost saving, we try to save all our small jobs to be done all at once rather that use a convenient rattle can. No matter how good a rattle can job can look on YouTube, its feel, durability, scratch and chip resistance are not up to par. Quite simply put, rattle cans do not put out enough paint for a proper application, nor do they use the right chemicals to ensure appropriate quality and durability.
What about heat resistant paint? Ever noticed how these so-called heat resistant paints are only available in spray cans? Google it. You won't find any commercial options for use in a spray gun. Does it work? Yes. And no. A spray can is ultimately a 1K system. It does not require a second ingredient such as a hardener to provide durability. Instead, spray cans rely solely on their 1K chemical makeup for adhesion and durability. Which is less than desirable. The heat resistant paints are basically the same except they use different, more expensive chemicals to create adhesion and durability - ones that can withstand a higher temperature before the paint burns. Now here's the rub (again, pardon the pun): the heat resistance rating is only relative to the other "standard" non-heat-resistant paint that you buy in cans. The standard cans use even cheaper chemicals that will fry when exposed to heat.
Notwithstanding that heat resistant paints are in fact heat resistant to some degree (up to about 250 DegC), they are still of a lower quality when compared to the 2K-gun-grade paint system which is superior in every way. 2K paint systems are inherently heat resistant - they're even baked to cure! They are completely different systems. The myth comes about that you need these heat resistant paints, because of the way they are marketed.
Basically, the 1K non-heat sensitive paint-in-a-can is rubbish and the heat-resistant version is just slighting less rubbish. So why use a rattle can at all? It's cheap, fast, you can DIY and it's ok for applications that don't require a high durability and finish. Although we wouldn't use it here at OEM, it could still work for you. Not everyone has hundreds of dollars lying around to paint their frame or exhaust. So, it does have a place. For the serious restorers however, 2K all the way.
HOW TO PAINT YOUR ENGINE, EXHAUST AND BRAKE CALIPERS
Ok. Want to know a secret? Ever wondered how motorcycle manufacturers paint their exhausts black? They don't! They use a process called Electrophoretic Paint, electro-coating, E-Coat or EP for short. Electrodeposition works much like a plating process. The workpiece is immersed in a bath of charged paint particles which adhere to the metal.
EP is an electrodeposited semi-gloss black epoxy paint that provides high corrosion and chip resistance and a uniform thickness. It can also be used as a primer or a one coat finish. This explains why when the paint wears off an engine cover, you never see a multi-layered paint system underneath. EP is widely specified by motorcycle and automotive manufacturers for corrosion protection of steel engine components and to provide a 100% uniform coverage of componentry including to coat recessed areas such as inside tubes, cavities and channels. This means, it can be used to provide a superior finish to engine cases, cylinders, heads, rocker covers, brake callipers, exhaust systems and more!
For the restorer, there is one major problem with replicating this process to paint your exhaust - it is only economical when thousands of items are coated all at once. It is strictly reserved for a production line. These are no commercial EP coating shops that will paint your single exhaust or muffler as it is not commercially viable to do so.
Ok, so what's the next best thing?. Cerakote! OEM has several products in development that will utilise this process including exhausts, mufflers, hubs etc. There is bound to be a licensed Cerakote provider in your state or country and we highly recommend this one-coat process for parts such as engine cases, exhausts, hubs and brake callipers.