Galvanising and electroplating

[Crazymanneil]

Hey all,

Not sure if this belongs here or what but here goes.

Getting bracketry close to where I want it now so thinking about how to coat it to prevent corrosion. Galvanising seems a good job with low maintenance and a tough finish. There is a place near me where I could get it hot dip galvanised which seems the longest lasting solution though imparts a lot of heat into the component which can cause distortion. I'm not keen on that as more than a mm or 2 will throw out alignment of engine and transmission and cause belt wear etc. Anyone got this done before?

Other alternative is a kit I have seen for around £60 with the chemicals, instructions etc to do it via electroplating. This means there would not be heat involved although not sure if its as good a job as the coating does not seem to come out as thick. The advantage would be that I could do it at home and have plenty left to coat other things.

Either that or I just paint the thing and be done with it though after the work that's been involved I would not mind spending a bit of cash to keep it good for a few years.

Anyway, back to the garage...

N

[smokyjoe]

A product that I used successfully many times is a "cold galvanizing" compound that is really a paint product with a very high amount of zinc- the cans rarely arrive smooth as they slightly crush with their weight bouncing around in shipping! I'm sorry but my old brain won't let me remember the brand name, but I am sure it wouldn't matter as you probably have a different brand across the pond.

It is imperative to thoroughly degrease the parts and sandblast or glass bead blast the parts to get a pure steel surface for the product to adhere to. Then it can be sprayed or brushed on the part. It contains active chemicals to allow the zinc to chemically bond to the steel, much like hot dip galvanizing. I did a bunch of brackets for a playground 20 years ago and they show absolutely no signs of rust. The material will even "self heal" if scratched, just like "real" galvanizing. One drawback is that the metal settles in the can so if you are keeping it a while you have to invert the can periodically to mix it up. It is very hard to mix by hand and if it sets around for a while you will have one arm bigger than the other when you get done stirring it.

AHAH! I remembered the name, ZRC for Zinc Rich Coating or something like that, here is the link: http://www.zrcworldwide.com/p_zrc.asp

I originally bought this stuff to paint my 30' steel boat, but never got around to using it for that purpose. I've used it for everything else, though. Stands up excellent to road salt we have here in the US in the winter. I've painted over it with zinc chromate (a no-no nowadays but I've still got some left) or zinc phosphate primer after roughing the surface a bit with a Scotchbrite pad and then giving it a thin, transparent coat of zinc primer and then overcoating it with lacquer primer or other primers and topcoats.

[Diesel Dave]

I'd powder coat the parts, get a batch deal sorted for blasting and coating.

Electroplating can embrittle parts as they get hydrogen absorption.

There are lots of paint on products, including the new POR stuff from Frost automotive.

[Sphere]

I will lightly paint my frame and subframe, then ride it until winter, scrutinize for abnormal wear and then have it powdercoated. Lets just hope that will be the winter of 2010

[Crazymanneil]

hmm good points guys. i'd come across something about embrittling but not really read it so will go find it again. good point about zinc compound stuff, i've used it before on gates and it worked well. would certainly be quicker to organise.

n

[smokyjoe]

I am an avid hater of powder coating. For one thing the part is heated hot enough to burn off any oils, etc. then after bead blasting heated again to melt the plastic finish. The heating isn't done under very controlled conditions like heat treating and normalizing and parts warp and if the part was previously heat treated it'll destroy the temper. Then, it's thickness can't be precisely controlled and parts don't fit any more (the TV chopper building guys always fall into this trap!) Everything that I have that was powdercoated has peeled and rusted when exposed to wetness and especially salt. (trailer, trailer hitch, various farm implements, car frame parts and other odd pieces) I've received some nasty cuts from flaked powder coating, it'll cut like a sharp, rusty razor blade!

I'll take good bead-blasting, primer and paint any day. That's a good idea to paint your bike up and drive it for a while, That's what I am going to do too. I wanted to do a fancy pearl and metalflake paint job at first but it'll be thin black paint until the bugs are shaken out.

I know, everybody uses it and you've probably had good luck with your experience, but what can I say?

Just my dumb 2 pennies worth.

[oldbmw]

I had lots of stuff hot dipped galvanised when I built boats. It is great for preservation of steel, but it will add quite a lot of weight to anything that is light and has lots of surface area ( such as tube frames. You may find you dont have enough holes for air and drainage in a normal frame. Ensure the steering head tube inner and the swing arm bearing tubes dont get dipped.

Think this is one place where I wouldn't hot dip.

[mark_in_manchester]

Someone mentioned POR paint products available in UK from Frost's in Ramsbottom. I've used black POR15 (after using their 'metal-ready' phosphate primer) on a few bike frames, with generally good results. It flows very nicely, and as long as you don't cut through it (when it peels a bit like thin powdercoat), it appears very durable. It goes matt under UV - I've painted tanks and guards in it, then rubbed back and finished with spray-on black smootherite from a can, and got very good results - certainly good enough for a frame, anyway! Cost for a frame including primer is prob about 20-25 quid, and you'd have some left over.
Mark, Manchester, UK

[smokyjoe]

I've used the POR-15 with good results, too. My complaint is that the darn stuff sticks so good that the lids get stuck on the can and you nearly have to destroy the can to get it back open! Also, once opened the shelf life seems to be in weeks. I had the best results by bead blasting or sandblating the parts then coating with POR-15. I've never used their phosphate primer, but that sounds like a good idea.

I think that I am going to use regular old enamel on the frame as I want to be able to easily weld on brackets, change mounts, etc. as I try to "perfect" the thing.