Chromium plating

Claim 1

A METHOD FOR REDUCING THE LOSS OF FATIGUE STRENGTH FOLLOWING CHROMIUM PLATING OF AN ARTICLE OF STEEL HAVING A HARDNESS OF 33C TO 47C ROCKWELL AND A FATIGUE STRENGTH OF 70,000 TO 110,000 P. S. I., COMPRISING ELECTRODEPOSITING CHROMIUM ON THE ARTICLE BY PASSING A CURRENT OF 1/44 TO 6 A. S. I. TO SAID ARTICLE AS CATHODE IN AN AQUEOUS CHROMIUM PLATING BATH AT AT TEMPERATURE OF 130 TO 150* F., SAID BATH COMPRISING ESSENTIALLY 150 TO 250 G./1. OF CRO3, A SULFATE-CONTAINING COMPOUND AND A SILICOFLURIDECONTAINING COMPOUND EACH IN AN AMOUNT TO PROVIDE,AS CATALYSTS, 0.8 TO 2.5 G./1. OF DISSOLVED SULFATE,SO4=, AND 1.2 TO 5.0 G./1. OF DISSOLVED SILICOFLUORIDE, SIF6=, RESPECTIVELY, THE SUM OF DISSOLVED SULFATE AND DISSOLVED SILICOFLOURIDE VARYING WITH THE CRO3 CONCENTRATION AS FOLLOWER: AS THE CRO3 INCREASES FROM 150 TO 250 G./L., THE LOWER LIMIT OF THE SAID SUM INCREASES LINEARLY FROM 2.3 TO 3.8 G./L. WHILE THE UPPER LIMIT OF THE SAID SUM INCREASES LINEARLY FROM 3.7 TO 6.5 G./L., SAID PLATING TEMPERATURE INCREASES WITHIN SAID RANGE AS SAID SUM OF DISSOLVED CATALYSTS INCREASES, PLATING CHROMIUM ON THE ARTICLE TO FORM A DEPOSIT ABOUT 5 TO 15 MILS TICK, SAID DEPOSIT BEING CHARACTERIZED BY HAVING 1200 TO 10,000 CRACK-LINES PER INCH AND A COMPRESSIVE STRESS OF 0 TO -20,000 P.S.I., AND THEREBY PRODUCING A CHROMIUM PLATED ARTICLE OF HARD STEEL HAVING A FATIGUE STRENGTH OF AT LEAST 85% OF THAT OF THE ORIGINAL UNPLATED STEEL.

Claim 2

A METHOD FOR REDUCING THE LOSS OF FATIGUE STRENGTH FOLLOWING CHROMIUM PLATING OF AN ARTICLE OF STEEL HAVING A HARDNESS OF 33C TO 47C ROCKWELL AND A FATIGUE STRENGTH OF 70,000 TO 110,000 P. S. I., COMPRISING ELECTRODEPOSITING CHROMIUM ON THE ARTICLE BY PASSING A CURRENT OF 1/44 TO 6 A. S. I. TO SAID ARTICLE AS CATHODE IN AN AQUEOUS CHROMIUM PLATING BATH AT AT TEMPERATURE OF 130 TO 150* F., SAID BATH COMPRISING ESSENTIALLY 150 TO 250 G./1. OF CRO3, A SULFATE-CONTAINING COMPOUND AND A SILICOFLURIDECONTAINING COMPOUND EACH IN AN AMOUNT TO PROVIDE,AS CATALYSTS, 0.8 TO 2.5 G./1. OF DISSOLVED SULFATE,SO4=, AND 1.2 TO 5.0 G./1. OF DISSOLVED SILICOFLUORIDE, SIF6=, RESPECTIVELY, THE SUM OF DISSOLVED SULFATE AND DISSOLVED SILICOFLOURIDE VARYING WITH THE CRO3 CONCENTRATION AS FOLLOWER: AS THE CRO3 INCREASES FROM 150 TO 250 G./L., THE LOWER LIMIT OF THE SAID SUM INCREASES LINEARLY FROM 2.3 TO 3.8 G./L. WHILE THE UPPER LIMIT OF THE SAID SUM INCREASES LINEARLY FROM 3.7 TO 6.5 G./L., SAID PLATING TEMPERATURE INCREASES WITHIN SAID RANGE AS SAID SUM OF DISSOLVED CATALYSTS INCREASES, PLATING CHROMIUM ON THE ARTICLE TO FORM A DEPOSIT ABOUT 5 TO 15 MILS TICK, SAID DEPOSIT BEING CHARACTERIZED BY HAVING 1200 TO 10,000 CRACK-LINES PER INCH AND A COMPRESSIVE STRESS OF 0 TO -20,000 P.S.I., AND THEREBY PRODUCING A CHROMIUM PLATED ARTICLE OF HARD STEEL HAVING A FATIGUE STRENGTH OF AT LEAST 85% OF THAT OF THE ORIGINAL UNPLATED STEEL.