When rebuilding an older vehicle, the cost of chrome plating is a topic commonly discussed with much trepidation. The process, however, is a time-consuming one with plenty of hidden work, and once you know what’s involved, you’ll soon see that what you pay is well justified considering the end product you receive. The theory behind the process hasn’t changed for 60 years, after being initiated by Henry Ford, prior to that nickel plating was all the rage.
George from Advanced Chrome Platers (ACP) in Hamilton ran us through the process at his purpose-built facility, which is the same as most used by chrome platers around the country and the world. George likens the job to being a chemist, electrician, welder and a blacksmith all at once, and when you examine the process, you soon see why.
Electroplating can be defined as the deposit of a very thin layer of metal to a base metal to enhance or change its appearance. Unlike painting where the new surface is sprayed on, the chrome (and associated materials) is applied via the use of an electrical current, hence the term electroplating.
A plating bath is the name for what is essentially a giant tank, many of which are used throughout the chroming process. The baths are filled with a liquid with the desired metal dissolved in it, be it silver, gold, nickel etc.
The plating bath solution serves as a conductive medium and utilises a low DC voltage. The metal item that is to be plated is submerged into the plating bath and a low voltage DC current is applied to the bath.
The electrolytic process then causes the dissolved metal ions to attach to the surface of the metal being plated. The thickness of the electroplated layer is determined by the time the item is in the plating bath while the current is being applied and the amount of current used.
Sometimes the shape and contour of the item can affect the thickness of the plated layer. Metal objects with sharp corners and edges will tend to have thicker plating on the outside corners and thinner plating in the recessed areas. This is due to the corners being more exposed, therefore attracting more particles.
The pricing for electroplating services is determined by numerous factors such as the type of plating (e.g. gold, silver, chrome, etc.), desired thickness of the plating, the base metal (e.g. steel, copper alloys, aluminium), the rough dimensions of the object to be plated and the number of items to be plated. As an example, nickel costs around $16,000 per tonne, and on your average ’50s car, there’s around 12kg of nickel needed.
What people forget though, is that since the plating process does not hide or mask surface imperfections, plenty of time is involved in ensuring a flawless finish before the plating process itself has even begun. Ask anyone who’s had a bumper from a ’50s car chromed how much work was involved in getting the bumper straight and tidy prior to plating, and you’ll soon see where a large proportion of the cost goes, yet it’s amazing how many people seem to forget this when it comes to tabulating the bill.
Most plating businesses don’t just focus on chroming. Instead, they offer a wide range of services, including stainless trim repairs, metal polishing, anodizing, galvanizing and more. When rebuilding a car, such as the ’56 Cadillac we’ve followed the painting process of over the last few months, it’s the ability to repair and polish the stainless trim that is most useful. Most vehicles of the chrome era have more than their fair share of dents and scrapes in the trim work, and removing them is not a straightforward task. Instead, it’s one that involves plenty of skill and an even greater amount of time, which all adds to the costs involved, in the same way that panel beating and preparation add to a paint job. As you’ll see over the next few pages, it’s amazing what can be repaired to a flawless finish with the right knowledge and skills.
With each tank used in the process (as seen over the next few pages) having a current sent through it to activate the solution within, George explains to us that the monthly power bill for a plating business can be as high as $30,000 — another hidden cost that customers might not be aware of.
At ACP the process starts off with the job being checked in and photographed. For this a digital camera is used, and photos are taken of every individual piece showing not only the item itself, but any damage on the items for future reference. In the case of the 1956 Cadillac, there were over 50 pieces in total, for which various processes were required, due to some being steel, some being cast and some being stainless.
With the job logged, all items — cast or steel — that are currently chromed, or are to be chromed, are wired up to copper wire to conduct electricity from the bars that run above the tanks to the part itself.
The first of many tanks the part is submerged into is the stripping bath. This bath is made up of caustic soda and is kept at 75°C. The small round balls you see on top of the tank are simply there to try and prevent as much heat from escaping as possible. After a few hours (depending on the amount of paint and grease on the item), they are removed, rinsed and scrubbed in clean water.
Next the old chrome is removed to a cold caustic bath, this time it is electrified to 12 volts with a reverse charge. This makes the old chrome come off the item with surprising ease in just 10 minutes. The old chrome and stripped metals are not recyclable. Their removal are a major expense for any electroplating company as local council bylaw requirements (trade waste consents legislations) control how they must be disposed of.
Following this, the item is once again rinsed in a clean water bath. This process not only cleans the caustic soda off the item, but stops cross-contamination of the other baths. After all, each one has a variety of chemicals, all of which must be kept precisely at the required levels. Some platers, like George, are qualified at this, while others rely on independent chemists to make regular visits to keep the levels in check!
As you’ll see later in the process, a layer of nickel lives below the chrome, both old and new. It’s this layer that must be removed next. Think of it as stripping back the existing primer on a car before paint. If you were to plate straight over the top, you couldn’t guarantee the quality or longevity of the finish.
To remove the nickel, the items are placed into a concentrated 98-percent sulphuric acid bath for around 30 minutes. Again, a 12 volt reverse charge is applied, which causes the nickel to reverse-plate off the item. Upon removal, the item is once again rinsed.
Next up any rust is removed, the steel item is placed in an inhibited hydrochloric acid for a two-hour time period. The trim is then again rinsed and the acid neutralised.
The above steps are taken regardless of whether the item is made from cast metal, (like many trim pieces), or from steel (say, a bumper). If there’s any damage to the items in need of repair, this is where the process changes slightly.
For bumpers and solid steel items most platers will have an experienced panel off-sider; ACP’s go-to guy, Mike, has 30 years’ of ‘hammer and file’ experience, and all the tools and tricks required to straighten bent metal back to perfection. The before shot of this bumper shows just how twisted it is on the underside. With the metal on these old bumpers being so thick, it takes a great deal of skill to work it, along with plenty of heat to help soften the metal. Of course, when you bend metal one way — say up or down — its natural reaction is to shrink or stretch across too, so to get it right, you must know how the metal will react. Straightening the bumpers alone consumed around nine-and-a-half hours, but the end result were bumpers as straight as they came from the factory 56 years ago. Unlike traditional panel beating, there’s no hiding anything, there can be no bog, weld lines or imperfections that paint will hide.
Cast items generally don’t get damaged, as they’re not used in high stress areas. However, on occasion they can be broken, as was the case for one of the front-quarter window surrounds for the Cadillac. Whilst welding cast parts isn’t generally recommended, with the right welding rods and expertise, it can be a solution that gives fantastic results. What does often happen to cast parts is pitting. Again, with the right knowledge and experience, this is totally fixable. Take the before and during photos of this bonnet ornament for example. While there’s a few hours’ work involved in repairing items like this, it’s far cheaper than sourcing a replacement, if that’s even possible at all.
With repairs taken care of, the next step is the sanding (linishing) stage. Many different grits are used starting with a coarse (60-grit) through to a fine (400-grit), with great care taken to get an even finish across the whole item, no matter how tricky it is. Areas such as the rear side of the bumpers do not go through the polishing process, just the faces which will be chromed and visible upon completion.
With the initial sanding sorted, it’s on to another workstation, where a buffing compound is used on a polishing wheel and the process continues. Three grades of polishing compound are used during this stage (600-, 800- and 1200-grit) to achieve a mirror finish. Depending on the size of the item in question, the average polishing time for a ’50s bumper is between six and eight hours! The bumper is held to the machine not the machine to the bumper — can you imagine holding up a 20kg bumper up to a polishing machine for eight hours?!
The conductive copper wires, which were removed for the polishing stage are now refitted, as are non-conductive weights to help keep the items from moving around in the solution due to tank agitation (such as bubbles).
To ensure all polishing compounds are removed the items are once again dropped into a hot caustic bath for around 30 minutes. If any compound is still on the items, not only will it contaminate the baths for the next stage, but it will also cause visual imperfections in the chrome finish. A rinse along with a thorough scrub is the final check before the items are moved to the next bath.
That next bath is a two-minute dip in a cold cyanide solution, where the parts are electro-cleaned by having a reverse charge put through them. Again, a fresh-water rinse is performed prior to the next stage. The items must not dry out before being transferred to the next stage; if they do, blotching will occur, often the sign of a lack of care during the process.
A cold bath of 10-percent sulphuric acid is then used for two minutes to give the surface a key for the next step to etch to. This is essential to ensure that the cyanide-based alkali copper used next will adhere to the item as much as possible. Attached to the sides of the bath are baskets with blocks of pure copper (anodes). When dissolved in the solution, the particles are attracted to the positively charged item, and soon a thin coat of copper covers the whole thing. The copper is less than one-micron thick and acts as a primer/sealer to key-in the next layer of plating.
Again the item is rinsed, then dropped into a 10-percent acid etch for 10 seconds, followed by a further rinse.
A bath of blue phosphorus copper sulphate solution is where the item will be placed next. This is used to cover the surface and will fill any microscopic imperfections. The bath is kept at an ambient temperature, and after the items are in it for 45 minutes they will come out with a coating of around 30 microns. Again, the copper (anode) is in baskets around the side of the bath and they look almost like copper ball bearings.
After yet another rinse — that’s eight rinses so far if you lost count — the items are back into the polishing shop, where a further 15 minutes of polishing with 800- and 1200-grit compounds will remove any residual defects.
Again, the copper wires and weights are reattached after being removed for polishing due to the risk of being caught in the polishing wheels. The same soaking procedure used above is then done again.
Rather than water, an alkali rinse is performed before the items are dropped back into the cold cyanide at 12 volts for two minutes, and rinsed again in water.
Another two-minute dip in the acid etch and another quick rinse is all the items need before they can finally make their way to a 45°C cyanide-copper mix, where they will sit for five minutes with 12 volts passing through them. During this time, they’ll form a smooth skin, which once again must be etched by a further two-minute dip in the acid etch, and rinsed.
So far, the compounds used in the process are relatively low cost. The nickel sulphate, which the items will spend the next 60 minutes sitting in, is markedly more expensive — in fact, it’s the most costly consumable of the whole procedure. After 60 minutes with a six-volt current, a 45-micron coating will be applied to the item. This is the most important part of the whole process, as it’s the nickel that gives the finished product its shine. Often the difference between cheap chrome and good chrome is the amount of time the items sit in this bath for. The difference is noticeable to the naked eye by the depth of colour in the finished item.
A rinse then removes any excess residue and prepares the item for the chrome itself, which is a comparably cheap and quick part of the whole procedure. Despite being orange itself, the chromic acid is what gives the bluish look, and after just four minutes in the bath with a 12-volt current, a three-micron coating will be fixed to the item. Again, the balls in the tank are there solely for insulation purposes. The tank itself is tested twice daily for correct chemical levels, brightness and condition, and is stirred throughout the day. After all, the chrome is a heavy metal so it tends to sink to the bottom when left for long periods. It’s noteworthy that a full refill of all the tanks used would set a shop the size of ACP back around $365,000, so thankfully they don’t require complete replacement all that often.
Once the items are removed from the tank, they’re given another quick rinse and the chrome-look that we all know and love appears from underneath the orange liquid. After a total of 25 steps and around seven hours, the product is nearly ready to be handed back over to the customer, but not before the dedicated quality control officer has had a good look over it to ensure that it’s perfect, and has given the item a polish by hand. The items are then checked against the job sheet, and packaged, ready to be collected.
The time taken for the process varies due to the size, shape and complexity of the item, as does the amount of voltage used in the various stages. Whether the job is a ’50s bumper or a safety pin it still has to go through all the plating processes, there are no short cuts.
The only way to know how long each item requires is by having years of experience and practice. George himself has been in the game for 36 years, and some of his staff have been with him for almost as long, making them quite possibly the most knowledgeable team around.
With so many details, and so much attention to them required, you can imagine the reaction to the risible situation of customers walking in thinking they can wait while their parts are chromed (a daily occurrence at most platers around the country). The reality is the process is as involved, if not more so, than painting a vehicle. And likewise, you get what you pay for. A low-cost job most likely indicates steps are being missed along the way, or steps are being rushed through to cut down on costs.
With stainless trim repair often being lumped under the umbrella of ‘chroming’ when vehicles are being built or restored, we thought it worth mentioning the process involved here too. Like repairing the steel bumpers, the process of fixing dented and scuffed trim is a time-consuming one, requiring a great amount of skill. Each individual dent is pressed out and slowly the metal is massaged back into shape. The perfect example of what can be achieved is the trim on these wheel spats. While almost anything is possible, some trim isn’t financially feasible to repair if it’s seriously damaged — although, if the parts are rare and irreplaceable, in the hands of an expert, it can be done. All the stainless trim on the 1956 Cadillac took around eight hours to straighten and repair — thankfully most of it was in good condition.
Once repaired, the items are polished using the same techniques as in the chroming process, with finer and finer compounds used towards the end of the procedure. The result is an almost mirror-like finish, which is as good as (if not better than) new.
This article is from NZV8 issue 88. Get your copy here.
Thanks to George and the team at ACP for their help with this article. You can find out more, and view pictures and videos of the plating process at www.plating.co.nz.
Here are some other professional chrome-platers in New Zealand.
Zinc and Chrome Ltd, Custom Plating to lower North Island www.zincandchrome.co.nz
Bumper Replacements NZ Ltd
Auckland / Christchurch / Blenheim / Dunedin / Invercargill / Napier / New Plymouth
Words: Todd Wylie Photos: Adam Croy[Gallery not found]