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This article was first published in 1999.
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Just about any metal component of a car can be brought up to look buffed by the simple process of polishing. And one of the big allures of polishing is that it is so cheap!
When you're cruising around at car shows, you can always be assured there'll be one engine bay that stands out from the rest. You know, the one with a fresh lick of paint, concealed wiring, braided hoses and, of course, an abundance of glimmering polished metal. But that polished metal isn't just a nicety reserved for the car show lads. One big attraction of polishing is that it is so cheap - and furthermore, just about any metal component of a car can be brought up to look buffed.
To set the foundations for you, it's quoted that "the polishing process is where dull or corrosion pitted metal is transformed into a smooth gloss surface". This smooth gloss finish can then be left bare, lacquered to provide lasting protection, or even sent off to be plated (eg chrome or gold plated, etc).
Just about any metal-based part of a car that can be pried off can be polished to a brilliant shine. The only requirement is that the part is in (or can be brought up to) sound condition. Some of the more common components Adelaide's A Class Metal Finishers Pty Ltd polish up for their customers include aftermarket wheels, pipes, rocker covers and even motorcycle mufflers.
How Do the Professionals Do It?
Conventional Polishing
The very first step towards getting your part polished (don't be rude!), is to find out what sort of condition it is in. Brand new parts shouldn't cause any hassles, but used ones can require some repairs prior to any polishing occurring. Often, rusted or damaged surfaces are found hiding beneath a layer of paint - tthis needs to be tended to first of all. This restoration can involve careful machining to remove problem areas, or in worst case scenarios, copper plating to fill-in small pits in the part.
Once a metal part (though not yet aluminium) is determined to be in good condition, it goes for a swim in a bath of solvent stripper. This eats off any paint, grease, grime and other impurities to return the metal to its untarnished raw base. A 100% clean part is a prerequisite to ending up with a good finish. However, one alternative to dipping the part in a solvent bath can be to have it glass bead blasted with fine beads. This gives a similar-ish result, but it's generally less effective and it can cause some minor damage to the part. In general, aluminium parts need to be glass bead blasted or sent to companies specialising in stripping paint from aluminium. Once taken back to its purest form, the chosen part is then moved on to be finished and polished.
At this stage, depending on its surface roughness, the part can be put against an emery linishing belt - beginning with a coarse grade and gradually working down to the finest. The steps are typically 80, 120, 150, 240 and 320 grade.
After the component has been smoothed with 320 grit, it is then ready for the polishing process. The machine operator firstly selects the right sized polishing wheel to get into all the nooks and crannies of the part, and sets about bring up a shine using a relatively harsh wax compound. During any one job, it may be necessary to change the polishing wheel size several times to reach into all the crevices.
A sisal wheel (a hand stitched "rag wheel") is used in conjunction with a softer wax block to remove any fine scratches. And finally, a "finishing mop" (which is an extremely soft cotton wheel) is used with another softer compound wax to give the ever-shiny end product.
It's largely the labour time involved in the linishing and polishing processes that dictates how much the end price is - but as a guide, these dual pipes took around 30 minutes on the polisher. Steel objects generally take the longest to polish, whilst aluminium (because of its relative softness) is considerably more compliant and swifter to bring up to a shine.
Electro Chemical Etching
Stainless steel parts are the only ones found on a car that can be treated to electro chemical etching (sometimes simply called electronic polishing).
Here, parts such as these CB radio aerial springs are immersed in a sulphuric acid based chemical bath, and have an electrical current sent through them. The actual level of current depends on the size of the object, but it isn't uncommon to run a couple of hundred amps through a part the size of a wheel. It's this current that removes a fine layer of the surface material to bring up a shiny new one. One major advantage of this method of polishing is that it is ideal for getting into difficult spaces of intricate parts. However, it does typically remove about 5 microns of the surface.
End Result
Once completed, the appearance of the shine of the newly polished part will depend on its composition. The two main factors that effect this are its silicon and magnesium content, but you can never really anticipate exactly what the part will look without actually trying it out. In most cases though, the variation of the shine of two different parts is fairly minor.
Here is how that stripped aftermarket rim looks after it had been polished.
What we can do to keep it lookin' sweet...
Once the part you've had polished returns to you, there are a couple of easy steps you can take to keep it looking A1. Giving it a generous coating of lacquer is widely suggested to protect the surface from scratches, but one downside is that it doesn't last all that long (depending on the environment). It can also cause problems when the lacquer gets chipped off, because the part then really needs to be re-stripped and re-polished to restore it. On the other hand, a non-lacquered part that's been scratched can simply be re-polished (or re-linished as well, if necessary). A Class Metal Finishers recommend using a silicone based wax, such as Mr Sheen, to keep a shine up (in the same way a paint wax does).
Heat can cause some discolouration if the part isn't regularly maintained through regular cleaning. For example, a polished stainless steel exhaust tip can quickly loose its shine if neglected, but if you're dedicated enough to keep it clean at all times, it should last nearly forever.
We should also point out that most parts can either be chrome, gold or silver plated - to name just a few. This provides extra protection for the part and generally requires less maintenance, but note that some metals should be zinc passivated before plating. This really is another story altogether, and you should talk to your entrusted plater before you tackle any job.
How much do you get slugged?
No matter how you look at it, getting parts for your car professionally polished gives an excellent visual upgrade at minimal cost. For example, a typical aftermarket wheel (depending on the complexity of its design and its condition) can cost anywhere in between A$50-100, while rocker covers for a V8 cost about A$70 on average for the pair. As A Class stressed to us though, the final cost will depend largely on the condition of the part, and the time that it takes to linish and polish it. But if you ask us, it's virtually always guaranteed to be an aesthetically uplifting bargain.
Contact:
A Class Metal Finishers Pty Ltd (Adelaide) +61 8 8384 4331
http://www.aclassmetal.com.au/
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