When it comes to laying surface coatings to protect the metal on our cars, solvent-based wet paint is but one option. There are many ways to treat metal to seal it from the elements, coat it for improved performance, or lay down a more visually appealing finish.

First published in the April 2024 issue of Street Machine

The coatings detailed here are specialised products and services, so they’re not necessarily going to be available in every industrial area of downtown Dunedoo. However, the coaters who can offer these services and products are worth hunting down, and it isn’t too hard to find them using the internet.

HYDRODIPPING

Wet paint and powdercoating are great if you’re after a uniform colour, but there is a way to have patterns applied to jobs, and this is known as water-transfer printing, immersion printing, or hydrodipping.

Hydrographic processes can be applied to metal, wood, plastic or glass, while the patterns are limited only by your imagination.

Serial feature-car-builder and former SMOTY winner Mark Sullivan runs PROcoat Hi Temp Ceramic Coatings in North Wyong, and previously offered hydrodipping services.

“[Hydrodipping] is pretty involved,” he says. “There is a base coat colour the job needs, and the water in the immersion tank must be at a certain temperature. You lay the pattern film on the water, then use an activator on the film, submerge the job, and then wash it off with water very thoroughly.

“I’d leave the job to dry, so the chemical is outgassed, and then it is right to seal with any automotive [2K] clear coat. After that it’s as durable as paint on the car.”

An attraction to hydrodipping is the ability to transfer detailed artistic designs and prints onto three-dimensional shapes.

“You buy the print by the metre and there are hundreds of designs: skulls and bones, flames, graffiti, zombies, brushed aluminium, carbonfibre, woodgrain, and more,” Mark says. “But hydrodipping just takes too long to do as a job, so we sold that side of our business off.”

ANODISING

Street machiners will be most familiar with anodised metals in the form of aluminium AN hose fittings, normally in the iconic bright blue or red colours.

Anodising is technically described as a process of electrolytic passivation, which is a fancy way of saying an acidic electrolytic solution has direct current put through it to coat the piece of metal sitting within.

Once it is done in the liquid, the part goes through a sealing process to prevent corrosion and lock in any dyes used to colour the job. Sealing can involve immersion in boiling deionised water, or a room-temperature nickel and fluoride bath.

Anodising is highly corrosion-resistant like powdercoat but is also micron-thin, making it perfect for fine-tolerance parts like AN fittings, keys, and engine components. Anodising is also claimed to help reduce the risk of galling in soft metals, like those used for aluminium AN fittings.

The red, blue and black AN fittings we’re used to seeing are coloured with dye added to the bath’s acidic solution, which leaves a uniform coating. Colour options for anodising are typically limited to basic, primary hues due to the costs involved in dye production, and the risk of fading with some colours. Interestingly, due to its molecular size, white is not a dye colour offered.

As with trick two-colour fade powdercoat jobs, there are ways to leave special effects in an anodised finish, including splashing darker colours onto a lighter base, but they are comparatively limited.

POWDERCOATING

Powdercoating uses dry powder, which is dusted onto a metal surface using compressed air and an electrostatic charge before being put through a bake cycle to cook it hard. Typically found in industrial settings due to its excellent protective capabilities and fast curing, powdercoating has boomed in the automotive industry, becoming a popular choice for all sorts of metal parts like wheels, bull-bars, 4×4 canopies, rocker covers, intakes, inner guards, and intake or intercooler piping.

Damien ‘Chubby’ Lowe from Lowe Fabrications powdercoats in-house, on both his own fabricated metal products and customer-supplied jobs. He is quick to outline some of the benefits of the dry-powder-based procedure.

“The durability of powdercoat beats wet paint,” Chubby explains. “It’s also an easier process to complete: once you’ve got the system set up you can have something blasted, coated, baked, and ready to fit in the time it takes to wet-rub a part for wet paint.”

Another benefit to powdercoating is the range of finishes possible. On top of gloss, satin, and matte surfaces, wrinkle textures are commonly available in a range of colours, while special effects like candy and Dormant powders offer eye-popping colours. This was one reason Chubby began offering powdercoating at Lowe Fabrications nearly a decade ago.

“I reckon we’ve been powdercoating for eight years now,” the noted Commodore expert says. “I was making my own products and getting them coated by someone else, but I wanted to bring them in-house so I could offer my customers custom colours on these parts; then I realised there was a market for offering powdercoating for car parts as well.”

While the options for automotive coating are almost limitless if the part is made of metal (look at Scott Barter’s powdercoated ‘56 Chevy pick-up in the 2020 SM Yearbook), Chubby finds he’s busiest with undercarriage and engine bay components.

“We mostly do suspension components, rocker covers, inlet manifolds, and brake calipers for customers,” he says. “This is in addition to the catch cans, wheel dollies, and fuel tanks we make in-house.”

Though it makes for a hardy, durable finish, the light depth of the powder can cause issues for those wanting a glass-smooth show car finish from their jobs. As Chubby says, this is partly because spraying powder isn’t like spraying 2K paint.

“It’s a different process,” he explains. “Jason, my brother, is a painter by trade and he had to learn the best ways to get the powdercoat laid flat on jobs, but it still isn’t as smooth as what you could get with paint. If you’re building a top elite car, you’ll probably need wet paint on the undercarriage to get that Grand Champion-level of flatness to the finish. That said, there are plenty of elite cars which have a lot of powdercoating on them, and it’s perfect for street cars.”

Caring for powdercoat is easy. Just like with paint, soapy water is the best way to clean coated parts. Some coaters will recommend using an aerosol glass cleaner to give the powdercoat a bit more shine.

HOW POWDERCOATING WORKS:

Brake calipers are an increasingly popular option to score a powdercoated finish, so we followed Scott Barter from Oxytech Powder Coatings as he showed us the basics of colour-coating these Brembo stoppers with a specialty Dormant purple powder.

CERAMIC COATING

Ceramic coating has proven to be a great way to improve thermal efficiency of various exhaust-related parts, from headers to turbo exhaust housings, dump pipes and more. Applied as a liquid, the ceramic-polymer composite epoxy reduces engine bay temperatures and improves gas flow in exhaust systems when applied internally.

Some companies, like Cerakote, sell kits to apply a cosmetic ceramic coating to metal parts at home, but high-temp ceramics need to be applied by specialists. Marcus Armstrong from Hi Octane Performance Coatings in Rydalmere, NSW explains how far ceramic coating can go.

“Most ceramic coatings will handle 900-1000deg Celcuis,” he says. “We do the polished-silver ceramic on a lot of hot rod suspension parts for that chrome look.

“It is a wet coating we spray on, like paint. We apply it using what looks like a touch-up spray gun, so we can get into tight areas around the underside of piping and the like. For areas where access is limited, like inside an exhaust or intercooler pipe, we have a way to push the raw ceramic down there, too.”

Historically, a drawback to ceramic coating has been a limited range of colour options, but Marcus says this is improving. “There used to really only be blacks and silvers as colour options,” he says. “There is a much wider range of colours now, including reds and blues. However, not all colours have the same temperature rating as the blacks and silvers.”

Ceramic coating can be expensive, partly due to the labour required for a given job. “There is a fair bit involved to coat a pair of headers,” Marcus says. “Parts get degreased, cleaned and then baked out in an oven at 300deg for three hours. After that, they’re media-blasted, baked again to remove any moisture, coated, then baked for three hours at 300deg. Then, if it’s going to be a polished finish, they need to be put in the polisher for 45 minutes per bank.”

Despite the time it takes to complete a job, Marcus says he’s seeing a marked increase in the number of people chasing ceramic coatings. “We’ve been doing it for 14 years, and it’s becoming more popular. We do turbo housings, dump pipes, intake and exhaust manifolds, bearing housings, and lately we’re doing a lot of mining equipment, as ceramic coatings help avoid corrosion.”

CHROME PLATING

Chrome-plating is a process where a thin layer of hexavalent chromium is electroplated onto a metal part using a liquid bath. Typically, automotive parts are ‘triple-plated’, meaning the piece is plated in copper, then nickel, and then chrome.

It can be difficult to find a chrome shop these days due to the highly toxic nature of the chemicals involved in the process. Modern environmental and workplace safety requirements also mean the chrome applied today might not match the 50s and 60s stuff in terms of potential shine.

Parts need to be thoroughly cleaned and acid-etched with intense rinsing stages in-between, before they’re immersed in the plating bath and then run through the electroplating process. After this they’re rinsed again, then polished.

With the dangerous chemicals and time-consuming nature of chroming, it is an incredibly expensive process to undertake. Different metals being chromed will need different etching chemicals, including hydrochloric, hydrofluoric, and sulfuric acids.

It is important to note that many classic cars also feature highly polished stainless trim (not chrome), and polished trim panels on many 50s and 60s American cars will can be made from ‘pot metal’. This was a cheap cast alloy made from a wide variety of scrap, and it normally cannot be chromed due to its poor metallurgical state, porosity, and amazing ability to rust even in dry conditions.