Many highly stressed parts have for decades been routinely processed in acid baths, either for cleaning in preparation for other processes, or in the actual process, like electro-plating. Think fork tubes, shock absorber shafts, crankshafts (hard chrome in chromic acid), huge numbers of aerospace fasteners and parts (cad plating using nitric acid), including jet plane landing gear, etc. All sorts of critical parts are cleaned in an acid solution (pickling) before coating or painting. I find it difficult to believe there is any risk in doing the same to a Commando frame.
Ken