METHOD FOR APPLYING COATINGS ONTO SEMICONDUCTIVE METALS AND ALLOYS THEREOF Russian patent published in 1997 - IPC

FIELD: electrochemistry. SUBSTANCE: proposed method comprises step of oxidizing semiconductive metals and alloys thereof to be coated under pulsed anode-cathode conditions in alkaline electrolyte so that alternating positive and negative pulses have complicated shape and duration of pulses and pauses therebetween is 100-300 mcs. At initial time moment 0-7 mcs anode current density value varies from 0 to 800 A/sq.dm and remains constant up to moment 25-50 mcs, whereafter it changes jump-wise from initially set value up to value comprised within range 80-800 A/sq.dm, and during time period from moment corresponding to 25 =-50 mcs up to pulse end anode current density value varies from 80 to 800 A/sq.dm. Cathode current density value varies jump-wise during time period 0-7 mcs from 0 to 800 A/sq.dm and remains constant up to moment 25-50 mcs, whereafter it changes jump-wise from initially set value up to value comprised within range 50-800 A/sq.dm. Subsequently, cathode current density value varies from moment corresponding to 25-50 mcs up to pulse end within range 80-800 A/sq.dm. As alkaline electrolyte, method employs alkaline solution of alkali metal phosphates, borates and fluorides at pH=7-8, components being present in following weight ratio: phosphates 40-45 g/l, borates 30-35 g/l, fluorides 10-15 g/l. Oxidic layer thus-obtained is further treated in polymeric material solution. As alternative embodiment, alkaline electrolyte is represented by solution comprising: water glass 80-200 g/l, alkali metal hydroxide 5-15 g/l, finely dispersed powder of metal and non-metal oxides, nitrides and carbides 2-20 g/l. Oxidic layer thus-obtained is further subjected to polishing. EFFECT: effective method for electrochemically applying coatings onto semiconductive metals. 5 cl, 1 tbl