Wednesday, 8 June 2011
Pimp my Ride with some Chrome Rims
I like cars. And when you see a nice car (or some souped up Honda Accord like in the Fast and Furious Five aka the worst movie ever made) you might appreciate the car more. Those rims shine a block away and seeing rims on a nice car makes it all the better. To lightly paraphrase Chris Rock: 'We love rims. Put shiny rims on any car if you would let them. Guys would put rims on a toaster if you would let him. Look at those 22's they are spinning.... they are spinning....they spinning.....'
But what makes rims so much more awesome then the plastic hubcaps on your Ford? The chrome job! The chrome you can see the shine of it from a mile away. It looks clean and polished. Car enthusiasts and anybody that likes rolling rims can thank some predated chemists or alchemists for starting the initial endeavors that would take us to chrome plating.
We go back to the middle ages with quasi scientists called alchemists. Alchemists goal was to use something called the Philosophers Stone to change lead into gold. As you know this is impossible but later these alchemists turned into chemists leading the way into discovering new understanding of science during the industrial revolution (1760 to 1830).
As you know with any new discoveries and for the discoveries that will eventually get to chrome plated rims parallel events need to happen. This is why some science should never be arrogantly ignored while other science gets funding. If that were the case we would not get rims. Two parallel discoveries happened in addition to advancements in chemistry. The first was the discovery of chromium in 1779 by Vauquelin in crocoite (lead chromate ore) and the subsequent reduction of the chromium by reduction with charcoal at high temperature 19 years later. The second multiple events that occurred were from three scientists that played around with electricity Micheal Faraday (laws of electrolysis), Alessandra Volta (electric pile) and Humphry Davy (theory of chemical affinity and early electrolysis) in the 1800's. Their work got us closer to chrome plating but as you know many horse drawn carriages did not have rims so we had to wait another 100 years before you could get your 22's.
The earliest work for chrome plating was done by a Frenchman named Junot de Bussy in 1848 who made a patent for electrodisposition of chromium. Seven years later Bunsen published a paper on chromium followed by Geuther two years later in gottingen, Germany showing the first detailed account of chromium plating. The later uses trivalent chromium plating using chromic acid solution which may have contained residual sulfuric acid which keeps the trivalent chromium from oxidizing at the anodes. This is important as the sulfate-based bath that uses lead anodes that are surrounded by boxes filled with sulfuric acid (known as shielded anodes), which keeps the trivalent chromium from oxidizing at the anodes. However, like a lot of science he might not have done a thorough investigation about why it worked. It worked!!! This lead other researchers to further develop trivalent chrome plating (hexavalent chrome plating however was soon to be discovered).
The first chromium metal was obtained by electrodeposition in France. This first result was realized by electrolysis of an aqueous trivalent chromium solution, published and patented in 1848 by Junot de Bussy. In 1854, Bunsen studied the influence of the cathodic current density on chromium deposition using a hot chromium chloride solution, with separation (porous pot) of anodic and cathodic compartments. The importance of the separation between anodic and cathodic compartment was considered a major discovery for a long time and was further developed by others researchers, including Placet and Bonnet in 1901, Voisin in 1910 and Recoura in 1913. Another researcher, LeBlanc, concluded that he could not electroplate any chromium from solutions of chrom alum or chromium sulphate and there was much controversy about depositing any chromium from any solution. Sometimes failure leads to breakthroughs. In 1905 two researchers named Carveth and Curry who worked at Cornell University concluded that the findings of Palcet and Bonnet were in fact correct and they also produced chromium plate from chromic acid solutions. These discoveries made trivalent chromium processes available leading to some pretty nice rims. However, impurities in the metal, disposition of thicker coatings and in some cases color for decorative chroming led people to discover an alternivative method.
Bancroft in 1906: “ The real solution from which to deposit chromium is not chrome alum nor sulphate, it os chromic acid”. This lead to making the process of hexavalent chrome plating where you use a slightly different setup than the trivalent chromium plating. This process included higher temperatures, higher current density and lastly the bath must be maintained below 30 dynes (I will come to this in a second). So finally, finally, finally you got your nice rims (so you can put it on your 1993 Honda Accord with a racing stripe).
But your rims come at an additional cost. A hidden cost. The workers that work with this stuff can suffer extreme health effects if the hexavelent chromium is not maintained in the bath. To maintain it workers use fume suppressants that must be strictly regulated using a stagalometer or even better a tensiometer. Some chrome platers are using this tensiometer in Asia and the US to maintain the bath surface tension so hexavalent chrome does not go into the air destroying lungs tissue.
So buy those rims. Make them spin. Pick up some ladies with them. But just be reminded that over two hundred years of research and some workers safety went into making them.