Anodes for the protection of metal structures against corrosion

Claim 1

A PROTECTIVE SYSTEM FOR A FERROUS STRUCTURE IMMERSED IN SEAWATER, SAID SYSTEM COMPRISING A MAIN ANODE HAVING A SURFACE AREA OF 0.071 TO 0.033 SQUARE FEET PER LB. OF METAL, A PLURALITY OF ANODE PLATES LOCATED ADJACENT THE MAIN ANODE AND OF WHICH THE SURFACE AREA IS BETWEEN 0.261 AND 1.72 SQUARE FEET PER LB. OF METAL SO THAT THEY BECOME COMPLETELY CONSUMED BY THE ELECTROLYTIC ACTION DURING AN INITIAL PERIOD OF USE, SAID PLATES HAVING A SMALLER VOLUME THAN SAID MAIN ANODE AND BEING BETWEEN ONE EIGHT OF AN INCH AND ONE INCH THICK AND EACH HAVING AN TOTAL SURFACE AREA OF FROM 200 TO 2500 SQUARE INCHES, SAID PLATES HAVING SURFACE AREAS NOT LESS THAN 0.8 OF THEIR ORIGINAL SURFACE AREAS AFTER HALF THEIR VOLUME HAS BEEN CONSUMED BY DISSOLUTION FROM THE PERIPHERY INWARDLY, AND A METAL ROD-LIKE ELEMENT CARRING BOTH THE MAIN ANODE AND THE PLATES, SAID ELEMENT BEING RIGIDLY MOUNTED IN SAID MAIN ANODE, SAID MAIN ANODE AND PLATES BEING MADE OF METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM AND MAGNESIUM BASE ALLOYS, SAID PLATES BEING DISPOSED CENTRALLY AROUND THE AXIS OF SAID ELEMENT AT BOTH SIDES OF SAID MAIN ANODE SUBSTANTIALLY PARALLEL TO EACH OTHER SO AS TO SHIELD EACH OTHER AGAINST CORROSION AT THEIR JUNCTURE WITH SAID ELEMENT