The results of the corrosion test for washing and cutting fluids used in the process of gear-shafts production are presented. The test has been performed according to the DIN 51360-2 (Ford-test) and the PN-92/M-55789 procedures. Three cutting fluids and three washing fluids were chosen and their solutions in tap water (used in practice in the company) were investigated. On the basis of the obtained results it has been stated that the lower the fluid concentration, the stronger corrosion is developed. The concentrations recommended by the producer in the case of cutting fluids are properly chosen. For washing fluids two regions of concentration have been evaluated. The concentration recommended for rinsing is too low for protection against corrosion, while higher concentrations, for the washing process, are properly chosen, and corrosion did not occur.