Cold Zinc Galvanizing

[dstig1]

I need to make a couple of post bases, as the posts are not a standard size for typical hardware. It looks like the best method (with what I have on hand...) is to weld them up from plain old bar stock. These will get buried in concrete next year, so they need more than a rattle can of primer and black. I was thinking about using one of those cold galvanizing "paints" to get them protected, and then possibly painting. I have done some web searching and found some options. The one from ZRC looks pretty solid, but everyone has their claims of Super Awesomeness (tm) so who knows? Thinking of cold zinc then primer and some topcoat, but I see the zinc guys say "no alkyd containing paint to topcoat" which covers just about everything out there in rattle can land. I'm looking for tips, suggestions, experience, etc. Posts are 8 3/4" square. Open to other additional suggestions, but the posts are already on site, so I am not getting smaller or larger ones...

Thanks Welding crew,
Dave

 

[yomax4]

I've used cold galv. for primer many times and put rustoleum paint over it. Never had an issue. Lots of brands out there. I've used CRC, Rustoleum,Arc Air and Welco. All seem the same but may have different properties. I've even welded through it with fair results.

 

[dstig1]

Thanks. I ordered a can of the WRC stuff as nobody had anything locally. I was a bit surprised by that... I'm sure it will work fine. I may have to coat some parts before final weld as they will be inaccessible after I put the last couple plates on, so it will be time for the respirator for sure (heck, I almost always wear a respirator when welding anyways...)

 

[Gary Fowler]

ZRC brand is 98% zinc and is what we always used to do field repairs to galvanized parts after welding. It works really well. We (industrial construction folks) never paint galvanized so I cant speak to how well paint would adhere but I would think it would hold better on the ZRC than on the galvanized. It takes an acid etching on galvanized to make paint stay on which is one reason we never painted it. Galvanized doesn't need additional paint for protection.

 

[Texasmark]

I have used whatever is sold locally in the rattle cans; don't remember brands. Put on an ample supply. Worked for me.

Mark

 

[yomax4]

Also if you bury in concrete, There may not be any air in there and the posts wouldn't rust anyway. Only where they stick out.

 

[LD1]

It would cost more but for piece of mind, you could fab up the bases with stainless. Perhaps dig through a stainless scrap pile at your local supply to get it a bit cheaper?

 

[Reverser]

Also if you bury in concrete, There may not be any air in there and the posts wouldn't rust anyway. Only where they stick out.

That's what I was thinking. In all the pipe I've seen buried in concrete that have rusted through, the weak spot has always been where the post meets the concrete at the top of the ground. But still the post will last for many years before it rusts through. Many times it will be an old sign post that long outlasts the business they were advertising.

 

[Reverser]

It takes an acid etching on galvanized to make paint stay on which is one reason we never painted it. .

Many years ago, I skirted a building with galvanized roofing. I was thinking about painting it to match the building and was told that an old time way was to coat the galvanize with vinegar, then paint after it dried.

I put vinegar in a pump up sprayer and wet it down, and later painted it with the same latex house paint I used on the building. I expected it to flake off, but it never did. It was still on there when I sold the place 10 years later. I suppose the acid in the vinegar etched the galvanize well enough to paint.

 

[CNC Dan]

Also if you bury in concrete, There may not be any air in there and the posts wouldn't rust anyway. Only where they stick out.

Not just lack of air(O2), but the alkalinity of the concrete tends to passivate the steel.