Are there risks to copper from repeated acid cleaning

Yes. Repeated acid cleaning can damage copper and its alloys over time. The acid not only removes the carbonate patina but may also etch the copper surface, promote loss of copper ions, and degrade protective oxide layers. Also, if the cleaning leaves copper citrate or other soluble copper salts, this may lead to corrosion when re-exposed to air/humidity. Inhibitor studies show that copper citrate solutions form and that copper may corrode in citrate environments unless inhibitors are used.

Therefore frequent acid treatments may reduce the thickness of the copper metal or alter the surface finish, making it softer, thinner, or more reactive to oxidation. For antique copper vessels this is a concern because the original patina may be protective. Hence cleaning should be controlled, mild, and followed by rinsing, drying and protective coating.