Chrome n' Complication...Rossin gets a makeover
Chrome, along with steel tubesets is en vogue once again and while there’s no denying its allure when gleaming seductively in the afternoon sun, electro plating remains a nasty process and one that presents all manner of headaches when refinishing. Many myths surround electroplate, the most common being that copper is employed for corrosion resistance (it is in fact, used to create an ultra smooth surface for the latter layers of super bright nickel responsible for the characteristic mirror effect).
Columbus forbid chrome on its tubesets, which is ironic since most Italian frames from the late eighties were positively dripping in the stuff. After twenty-three years, this quite fetching and clearly well loved Rossin is due a makeover. Contrary to popular misconception, plating and enamel do not magically stop where the other begins and this overlap proves particularly troublesome. Paint shops have traditionally employed acid etch primers to forge a good bond but sooner or later, the livery looses.
In some cases, minute traces of residual acids can linger inside the tubes, resulting in premature frame fractures (a phenomenon known as hydrogen embrittlement- quite common to race rigs built from Reynolds 753). Mercifully this Rossin is crafted from Columbus Gara, a thicker, workman like Cro-moly, marketed at the training/touring audiences and better able to withstand various abuses in the first instance. Good quality electroplate is old boots tough yet vulnerable to pitting from shot-blast. Sickly peeling, tarnished stuff can be stripped by this latter abrasive and replaced by none other than chrome-effect epoxy powder coating. Purists may sneer but these days powder is good enough to pass for the original surface. Wet-spray two pac paints can then be used over the top for faithful “Factory fresh” results.
Since its only the enamel that needs removing, Graham laboriously mummifies the chainstay and fork legs in electrical tape and shuns the traditional blaster in favour of a mini cabinet that fires a less aggressive aluminium oxide. Vapour blasting is another alternative particularly suited to aluminium, magnesium and similarly soft metals because abrasive grains are passed over in a fine mist of water. However, in this context, it won’t provide the necessary interface for the chromate primer and final powder coat. The forks were originally half-chrome and light tell tale swirls indicate where the enamel has been previously removed so this must be keyed in the same fashion. Fifteen careful minutes later and the frameset emerges bare but unblemished, ready for masking and the zinc chromate primer.
Many job-lot finishers offer keen pricing but typically rush frames through with office furniture. In stark contrast, project sprayers will methodically mask-threaded sections so mechs, bottom brackets and other components can be refitted without fuss. Good quality powder coat will resist the forces of a hammer blow but if the chromate is omitted in the interests of cost-cutting, a stone chip could see moisture, salt and other nasties lurking beneath the outer skin, causing potentially serious corrosion and the paint to lift in ribbons (common to old Meriden built Triumph motorcycle frames thanks to diabolical quality control). By the same token, advise your chosen finisher if your frame has Waxoyl, mud, oil or similar contaminant sloshing around the tubes since this can rush from the drainage holes during the curing process, ruining your finish and those alongside it. Wet spray zinc primers and body fillers are also incompatible with powder coating-the latter retains moisture causing the foreign matter to explode in the oven.
Either address dents with brass/silver solder or Thermabond3, a dedicated maulable product capable of resisting temperatures of around 220 degrees. Electrical tape remains in situ to mask and protect the brightwork from unwanted over-spray and/or heat related discoloration. Being an electro-static process minimises wastage and means we’re oven ready in fifteen minutes, whereupon it assumes a liquid form. A clear lacquer topcoat would offer the last word in durability, especially on a winter trainer but even so, the fresh gloss black livery should remain beautiful for many years to come. Standard colours command £55 including blasting but the team at Maldon Shot blasting & Powder Coating advise more involved preparation pushes the finial cost to £75.
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|Rossin freshly blasted by the curing oven.jpg||31.75 KB|
|Rossin Gara reborn in gloss black powder coat.jpg||41.57 KB|