Jerome01

A 1-inch linear shaft like that is most likely a hardened steel shaft used for linear bearings, typically made from high-carbon bearing steel (such as 52100 or similar) with a hard chrome-plated surface rather than stainless steel. The blue-green color in the hydrochloric acid suggests the acid is attacking the chromium plating or trace alloying elements, while the areas where the coating was removed react differently because the underlying hardened steel is exposed. If you plan to forge it, it's best to completely remove any plating first and work in a well-ventilated area, as heating chrome-plated steel can produce hazardous fumes.