METHOD OF DETERMINING ENDING TIME OF CHEMICAL ETCHING Russian patent published in 1998 - IPC

FIELD: electric power plant equipment. SUBSTANCE: invention relates to chemical treatment of surfaces and may be applied in determining ending time of chemically etching refractory coatings when repairing gas turbine engine blades without affecting base material. Blades and reference electrode are immersed into etching solution and one measures potential difference between blade surface and reference electrode in the course of etching process, which is terminated when the following conditions are met: k=E_m/E_s≥1 where E_m is electrochemical potential of curve transition from the plane front to the drop for blades with operating time up to 100 h or potential value in the region of transition to the sharp drop for blades with operating time above 100 h, k=0.5-0.8 is a coefficient determined by operating time, and E_s electrode potential recorded during the etching process. EFFECT: facilitated determination of etching end time allowing base material cracking to be avoided. 1 dwg