would you find this acceptable? [instead of stubbing the ufer up through the foundation wall 12" above the bottom plate indoors,] stub the Ufer rebar out of the footing, outdoors exposed to the dirt and weather, with a typical ground rod connection made to this Ufer. pipes, conduits, and rods can be iron or steel, if the conditions are met in 250, but it seems to me that rebar doesn't really fit outdoors in a wet environment. i would expect it to rust and lose its value at the acorn or clamp connection. but we allow clamps to bond to galvanized water pipes and black iron gas lines outdoors, and you are supposed to scrape the coating off to make a good bond. go figure.
I would have a hard time accepting the exposed ufer connection for the reasons you are concerned about. As far as other piping I have never been required to scrape the galvanized coating off water piping and doing so would cause the plumber and plumbing inspector to have a fit. Black iron gas piping and fittings are not supposed to be installed where they are exposed to weather unless they are coated for protection. Again it would be a violation to remove any protective coating.
I would also not permit an acorn clamp to used to connect the grounding electrode conductor to the ufer. I have never seen one listed for this purpose and doubt there are any. Copper and steel should never be in direct contact with each other because of electrolysis. I don't have a problem with using standard brass or bronze clamps even thought most are also not listed for this purpose. I know most of the T&B U-bolt type ground clamps are listed for rebar.
Re: Ufer in dirt#13017 08/23/0205:39 AM08/23/0205:39 AM
We must live in a different world here in So CA. The AHJ's will only accept 20'or > of GEC sized (or larger) Cu as a Ufer. When bonded to the rebar, I do it with Cadwelds. Galvanized water lines? Haven't seen one in years, except on old buildings. Just Cu.