Metal touch up coating for galvanized hardware

[grousehunter]

When you (those of you who have) grind off some of a carriage bolt's head in order to slim it down as is done when bolting up the stem and forefoot, what is a good coating for the area that you've ground away, which would no longer have the protection of the zinc (galvanizing)? Is there a preference among paints/primers? Is there some type of rough equivalent (cold zinc coating in a can?).

Thanks,
Ed

[peter radclyffe]

galvafroid, red oxide or any good steel primer

[Mike Vogdes]

Cold galv spray.

[Bill R]

Cold galv. spray, or brush on. Available at any decent industrial supply house.

Not as good as hot dip, but much better than nothing or using regular paint of primer. We use it all the time on towers as a touchup. (most of my stuff is along the coast)

[Todd D]

I just used bronze. No worries about protective coatings.

[grousehunter]

Sorry I neglected to mention that this hardware is for a daysailer that, as long as I own her, will be in fresh water only.
I saw the Penetrol stuff in a Sherwin Williams store in town and the salesman was also quick to promote its utility and effectiveness.
Since the stem assembly will also be glued and I won't bung over the bolt heads with a graving piece for a long time, I think it would be interesting to bolt it up but in parallel do a little long term lifecycle testing of the protective coating on some extra bolts; maybe even drive one into a tightly fitted hole in a piece of oak and drown it for a month or so. If things don't look well I can slip the bolts out and replace with bronze.
Thanks all.
Ed

[Nicholas Carey]

Ospho -- http://www.ospho.com/

It's a phosphoric acid solution. It basically parkerizes (http://en.wikipedia.org/wiki/Parkerizing) both the steel and zinc, effectively giving everything a iron or zinc phosphate casing.