My SIII re-frame

[Apis Mellifera]

As I type, my new chassis is on a boat from England. Being galvanised, I like the idea of seeing it. However, the original only lasted 36 years. The new one should last much longer, but I don't want my 2.5 year old son's kids to have to change it again.

What say you? Paint or no paint?

Also, any "while you're at it"s? I'm looking for kunifer brake lines for a RHD boosted dual circuit 88...no luck so far. I've ordered new suspension and body mounting hardware. Most of the other stuff is already stainless.

[crankin]

No paint. I like the way that my rig is all galvy.

https://lh5.googleusercontent.com/-ExvzxDf2HJE/S6qkdKfKwMI/AAAAAAAABBg/UuMTC9uX40Y/s800/DSC04106.JPG

[LaneRover]

I have heard that painting galvanization actually reduces some of the effectiveness of the galvanizing process.

To make it really last forever make it out of stainless and THEN galvanize it! :D

[stomper]

This is a great question, as I have been considering painting my rear cross member black to match the original look, but I am not sure I want to cover the galvy. I will be watching this thread closely.

[jac04]

I painted the galvanized frame when I restored my old 63, just because I wanted it to look stock. Yes, painting over the galvanized surface will reduce the effectiveness of the galvanizing because the external zinc is no longer exposed. You also need to prep the surface properly or the paint will just flake off. When I restored my Lightweight I left the frame bare. I figured I would show off my galvanized frame.

[albersj51]

I'm considering the same thing. As I understand it, the protective quality comes from exposure to the air by turning zinc into zinc carbonate. If this takes place quickly, could you set it outside for a week or two to develop this layer then paint?

Also, if you painted it before this layer takes hold, wouldn't the zinc remain in its normal reactive state and form zinc carbonate if/when exposed to the atmosphere if the paint is chipped or scratched. If so, then the paint forms another layer of protection, right? Just thinking out loud here.

[Broadstone]

Yes, painting over the galvanized surface will reduce the effectiveness of the galvanizing because the external zinc is no longer exposed.

I would be quite interested in facts backing this up. Not to dispute or question any ones information on this but because this topic really interests me. I do see a fair amount of galvanized steel in my line of work and have seen it exposed, painted and even powdercoated.

Since HDG provides a zinc coating which is a barrier for water and oxygen and produces a cathodic or sacrificial protection for the steel. The zinc will be consumed first to prevent the steel from being consumed.

So if paint protects the sacrificial metal (zinc) from being consumed, how is it reducing its effectiveness.

[bkreutz]

From the American Galvanizing Association
http://www.galvanizeit.org/aga/specifying-inspecting/specifying-hdg-paint/

[jac04]

So if paint protects the sacrificial metal (zinc) from being consumed, how is it reducing its effectiveness.
If the zinc can't scarifice itself to protect the steel, then it isn't doing its job. Say you had a big steel plate that was galvanized except for a small 6" x 6" exposed area of steel. No problem, the zinc will sacrifice itself to save the steel. Now say you had the same galvanized plate, but you painted it except for a 5" x 5" spot in the center of the bare steel 6" x 6" spot. The 5'"x 5" area of exposed steel would be afforded no protection at all by the galvanizing. The paint "insulates" the steel from the galvanizing. This is obviously an extreme case, but the exposed surface ratio of bare steel to zinc has an impact on how effectice the galvanizing is.

[redmondrover]

Like others have said, don't paint it--it looks great galvanized!

As for the other question regarding "while you are at it," that is dangerous territory...we went there with the frame swap on my wife's 109. If you care to read about it, see the postings from November 2009 through August 2010 in the blog I kept redmondrover.blogspot.com