Chromium plating (usually known simply as ‘chrome’) has been a staple finish for BMX bikes and parts pretty much since the sport’s inception when I was little more than a glint in the milkman’s eye. Everybody from yours truly to your little brother has run chrome plated parts; rims being the steady favourite for generations (you can’t deny that it’s a classic look) partly due to being a harder wearing brake surface than anodizing. While it’s nice to have nice things, the horrible truth is that although chrome plating has aesthetic advantages, it has a far darker side behind the scenes.
The biggest structural flaw with chrome plated parts is in the structural steel components like frames, bars, and cranks and is caused by something called ‘sacrificial metals’. When electroplating a steel component, it is first negatively charged by an electrical source before being immersed in a chromic acid bath with a sacrificial zinc or carbon anode; of which is positively charged. The anode is (in layman’s terms) used to prevent the iron in your part from losing it’s electrons thus attracting oxygen molecules and turning into a lump of rust in the acid/electrolyte bath. The anode loses the electrons instead and it oxidises in place of the iron; this is a good example of a ‘sacrificial metal’. This technique is also used on cheap zinc-covered town-bike spokes, roofing and even for ship hulls.
Unfortunately there is a bad example too. If the necessary pre-treatments of stripping, cleaning, sanding, polishing, multiple layers of copper and nickel plating etc, etc aren’t done properly then there will be flaws in the chrome when it comes to chrome plating eg. porous texture, poor adhesion, perforations etc. While I use the word ‘flaws’, don’t think of them as cute, minor little flaws like a bubble in your grips or a small buckle in your rim; these are disastrous flaws that, if unchecked over long periods, can and may well maim you. Chrome plating keeps water away from the iron contained in the tubes of (let’s say for argument’s sake) your bars and preventing them from rusting as a barrier layer but the problem is that iron is anodic to the nickel in the same way that zinc is anodic to iron. The slightest perforation in the plating (of which can easily be caused by manufacturing or rider error; defective chrome plating, grinding, crashing, even simple installation can damage the plating if you’re not careful- chromium is plated by the millionth of an inch) not only makes the tubing vulnerable to rust but because iron is anodic to the plating itself, the rusting is actually accelerated by the chrome plating that’s supposed to be protecting it- the steel literally sacrifices itself for the chrome. This is why you’ll see old American cars with rusted out bumpers with the chrome peeling away where the steel has corroded underneath to the point where it’s barely there any more. This site is a good place for more information about chrome plating as a finish.
It doesn’t end there though, while searching for distribution info on the FlyBikes website last week, I stumbled across an interesting section on their frequently-asked-questions portion of the page;
While the structural (and weight) disadvantages of chrome has been more or less clear to me for years and usually steered me away from actually spending money on it, I had no clue of the environmental or the human cost of a mere finish.
Spotting that Flybikes FAQ explaining their wholly righteous reason for not offering chrome colour options prompted me to do some good old Google trawling on the negative health affects of chromium plating; there was a lot of material. This report by the Centre of Disease Control and Prevention was the most reliable literature I could find on the subject; being the CDCP is a government agency and the fact that the US chrome plating industry is pretty damn big so they probably know what they are talking about.
There are two different types of decorative chrome plating, trivalent and hexavalent; the stuff that made Erin Brockovich a household name. Unfortunately I can’t tell the difference scientifically because I only have a very limited understanding of these things but trivalent is basically ‘modern’ chrome, it has more of a nickel tint whereas hexavalent is the classic ‘old school’ stuff; harder wearing, blue-r tint but heavily regulated by the state and for good reason, hexavalent chromium is hugely toxic. It’s trivalent counter part is not quite as harmful, has less stringent exhaust regulations and is easier to waste treat; spilling a small beaker of it’s hexavalent counterpart on your garage floor has the potential to poison any nearby wells and land you in some deep trouble.
The gases emitted by the chromic acid are the super dangerous part about hexavalent chromium, without adequate fume-extraction or personal protective equipment, a chrome worker is subject to some horrific illnesses including but probably not limited to; cancers of the lung, trachea, and bronchus, contact dermatitis, skin ulcers, irritation and ulceration of the inner nasal lining (nasal mucosa) as well as perforation of the nasal septum- a symptom commonly associated with prolonged cocaine abuse. The CDCP findings also report of kidney damage, liver damage, pulmonary congestion and edema, epigastric pain, erosion and discolouration of teeth, and even perforated ear drums. In the case of the nasal ailments, on average the symptoms start manifesting within the first month of employment with a chrome plating shop.
This passage from the CDCP report was stood out to me as the most troubling though;
..11 male employees in an Ohio electroplating facility reported that most men had worked in the “hard-chrome” area* for the majority of their employment (average duration: 7.5 years; range: 3–16 years). Four of the 11 workers had a perforated nasal septum. Nine of the 11 men had hand scars resulting from past chrome ulcerations. Other effects found during the investigation included nose bleeds, “runny nose,” and nasal ulcerations..
*Hard-chrome is often known as ‘engineering chrome’ and is used for lubricity or oil retention in things like car engine parts and gun barrels. Although essentially the same as it’s decorative counterpart, it’s applied in thousandths of an inch rather than millionths like decorative chrome.
So what can be done? It depends on how much you like your chrome bike I guess, you could hassle your favourite companies via social media into telling you whether they’re using hexavalent or trivalent chrome (to the untrained eye it’s hard to tell the difference) and only buy trivalent if like me, your conscience is getting the better of you. You could even boycott using chrome parts altogether until there’s better identification of whether they’re using trivalent or not, there are plenty of adequate alternatives including fine polishing, anodising and even certain types of chrome-look paint that look great, come in more colour options, weigh less, are less harmful to the environment and are better suited to people who live in wetter climates. If you already have chrome parts, you can take better care of them by spraying something like J P Weigle’s Frame Saver into the inside of the tubes and generally keeping the outside of them clean with soapy water… and by not grinding. The choice is yours at the end of the day; vote with your wallet.