Frame Powder Coating / Metal Grain

Hi John,

   It looks like your frame has been shot-peened rather than sand blasted. This is normally a process to surface harden solid steel, but I don't think it works on frame tubes (?)

Hi john,

The  roughness of the frame could be down to it having been shot blasted before powder coating rather than sand blasted which leaves a much finer finish. Powder coating is good at covering this up but I also prefer the look of a painted frame. I did get a frame shot blasted once and had to spend ages sanding it down to get it smooth enough to paint. Having said that, the frame I have just painted with enamel seems to chip all to easily. I accidentally knocked over the swinging arm today and was thinking I maybe should have gone for powder coating!

Al. 

I'm lucky in having "Trestan Finishers" less than 2 miles from where I live in Southampton.  There you have a choice of stove enamel, powder coating or a range of spray finishes including 2-pack acrylic, polyurethane or epoxy.  They also do grit, shot and vapour blasting (which actually uses glass beads)  Norman Williams had a Dommie barrel awaiting collection (or delivery) when I went in once.  I asked what the shiny black finish was - stove enamelled!  They are used to working with bike parts - always a good thing.  It sounds like the people who did your frame didn't have much idea.  Shot-peening a frame is overkill and creates the problems you have found.

I went for 'original' stove enamelling after grit blasting of my frame and cycle parts.  Some parts needed further restoration, such as the mudguards, which resembled colanders in places, so they were blasted and etchant-primed.  To show you how good that is, the mudguards were done about 10 years ago with no topcoat and there is still no sign of rust!  This is in spite of no rust-killer being applied. I lent the rear guard to Restoration Spares for a few years to copy. Very complex with its detachable tail section and separate side valances.  Quite a work of art to fabricate by hand nowadays.  That's why they are so rare to find as reproduction items.

Powder coating has that "plasticky" feel, mainly because it is plastic!  The method was borrowed from photocopying, which uses fine plastic powder, electrostatic energy and heat. It is susceptible to rust-worm wherever it is damaged so is difficult to touch-up, unlike enamel which, although it will chip, the worm doesn't get under its skin easily.  I would always go for enamel for any exterior surfaces.  Powder-coating can hide rust whilst it eats its way along and in, like woodworm!

I notice a remark or two about applying etch coat on top of a previously applied coat of 'anti rust paint'. Surely the etch coat should be applied first to the clean bare metal?