The purpose of the study was investigation of the electrochemical properties of chromium-nickel alloy which are changed during mechanical processing associated with the preparation of pressed crowns. The laboratory procedures (polishing excluded) exert a harmful effect on the electrolytic potential of the alloy. The procedures are only intermediate phases and are without any significant role, since the end-result is, after annealing and polishing, as expected. However, mechanical processing in dentist's office is quite different. Of interest are the poor results obtained in such mechanical procedures as overbending and becking. These procedures should not be done in dentist's offices also for other reasons.