Chromium plating

Claim 1

A METHOD OF ELECTRODEPOSITION CRACK-FREE, CHROMIUM PLATE ON AN ARTICLE OF METAL WHICH COMPRISES ESSENTIALLY: PASSING CURRENT IN THE RANGE OF 0.5 TO 8 AMPERES PER SQUARE INCH FROM AN ANODE TO SAID ARTICLE AS A CATHODE IMMERSED IN AN AQUEOUS CHROMIUM PLATING BATH AT A TEMPERATURE OF 140* F. TO THE BOILING POINT OF THE BATH, SAID BATH COMPRISING ESSENTIALLY 200 TO 900 G./L. CRO3, STRONTIUM SULFATE AND AN ALKALI METAL SILICOFLUORIDE EACH IN AN AMOUNT SUFFICIENT TO SATURATE SAID BATH AND TO PROVIDE THEREIN AN UNDISSOLVED RESIDUE OF STRONTIUM SULFATE AND ALKALI METAL SILICOFLUORIDE, RESPECTIVELY, SAID ALKALI METAL BEING SELECTED FROM THE CLASS CONSISTING OF POTASSIUM AND SODIUM, A SOLUBLE NON-CATALYTIC STRONTIUM COMPOUND IN AN AMOUNT SUFFICIENT TO ADJUST THE CONCENTRATION OF THE STRONTIUM SULFATE IN SOLUTION IN SAID BATH TO 0.3 TO 5.5 G./L. OF SULFATE (SO4=), AND A SOLUBLE NON-CATALYTIC ALKALI METAL COMPOUND IN AN AMOUNT SUFFICIENT TO ADJUST THE CONCENTRATION OF THE ALKALI METAL SILICOFLUORIDE IN SOLUTION IN SAID BATH TO 1.0 TO 11.4 G./L. OF SILICOFLUORIDE (SIF6=), THE SUM OF SAID DISSOLVED SULFATE AND SILICOFLUORIDE BEING IN THE RANGE OF 1.5 TO 11.7 G./L., SAID SUM OF DISSOLVED SULFATE AND SILICOFLUORIDE VARYING WITH THE CRO3 CONCENTRATION IN THE MANNER DEFINED BY THE AREA ABCD OF THE GRAPH SHOWN IN THE ACCOMPANYING DRAWING, THE ALKALI METAL OF SAID NON-CATALYTIC COMPOUND BEING THE SAME AS THE ALKALI METAL OF SAID ALKALI METAL SILICOFLUORIDE.

Claim 2

A METHOD OF ELECTRODEPOSITION CRACK-FREE, CHROMIUM PLATE ON AN ARTICLE OF METAL WHICH COMPRISES ESSENTIALLY: PASSING CURRENT IN THE RANGE OF 0.5 TO 8 AMPERES PER SQUARE INCH FROM AN ANODE TO SAID ARTICLE AS A CATHODE IMMERSED IN AN AQUEOUS CHROMIUM PLATING BATH AT A TEMPERATURE OF 140* F. TO THE BOILING POINT OF THE BATH, SAID BATH COMPRISING ESSENTIALLY 200 TO 900 G./L. CRO3, STRONTIUM SULFATE AND AN ALKALI METAL SILICOFLUORIDE EACH IN AN AMOUNT SUFFICIENT TO SATURATE SAID BATH AND TO PROVIDE THEREIN AN UNDISSOLVED RESIDUE OF STRONTIUM SULFATE AND ALKALI METAL SILICOFLUORIDE, RESPECTIVELY, SAID ALKALI METAL BEING SELECTED FROM THE CLASS CONSISTING OF POTASSIUM AND SODIUM, A SOLUBLE NON-CATALYTIC STRONTIUM COMPOUND IN AN AMOUNT SUFFICIENT TO ADJUST THE CONCENTRATION OF THE STRONTIUM SULFATE IN SOLUTION IN SAID BATH TO 0.3 TO 5.5 G./L. OF SULFATE (SO4=), AND A SOLUBLE NON-CATALYTIC ALKALI METAL COMPOUND IN AN AMOUNT SUFFICIENT TO ADJUST THE CONCENTRATION OF THE ALKALI METAL SILICOFLUORIDE IN SOLUTION IN SAID BATH TO 1.0 TO 11.4 G./L. OF SILICOFLUORIDE (SIF6=), THE SUM OF SAID DISSOLVED SULFATE AND SILICOFLUORIDE BEING IN THE RANGE OF 1.5 TO 11.7 G./L., SAID SUM OF DISSOLVED SULFATE AND SILICOFLUORIDE VARYING WITH THE CRO3 CONCENTRATION IN THE MANNER DEFINED BY THE AREA ABCD OF THE GRAPH SHOWN IN THE ACCOMPANYING DRAWING, THE ALKALI METAL OF SAID NON-CATALYTIC COMPOUND BEING THE SAME AS THE ALKALI METAL OF SAID ALKALI METAL SILICOFLUORIDE.