LEAD-PLATINUM PROTECTS BART'S TRANS-BAY TUBE
SPECIAL LEAD-PLATINUM BI-ELECTRODES ARE USED AS ANODES IN THE LARGE-SCALE CATHODIC PROTECTION OF THE BAY AREA RAPID TRANSIT SYSTEM. THE ELECTRODES CONSIST OF SMALL PLATINUM INSERTS EMBEDDED IN LEAD RODS. INCLUSION OF THE PLATINUM CAUSES A CONSIDERABLE CHANGE IN FUNCTION OF THE LEAD AS AN ELECTRODE. ANODIC POLARIZATION OF THE COMBINATION ROD CAUSES THE FORMATION OF HIGHLY CONDUCTIVE LEAD PEROXIDE ON THE ROD'S SURFACE, RESULTING IN INCREASED FLOW OF CURRENT AND CONSEQUENT IMPROVEMENT IN THE PROTECTIVE EFFECTIVENESS OF THE SYSTEM. THE SYSTEM CONSISTS OF 16 LEADED-PLATINUM ANODE ARRAYS PLACED ON BOTH SIDES OF THE TUBE APPROXIMATELY 100 YARDS FROM THE STEEL SHELL. THE ANODES REST ON CREOSOTED WOOD PLATFORMS 5 FT HIGH AND 30 FT LONG. CONCRETE BALLAST HOLDS THE PLATFORMS IN PLACE ON THE FLOOR OF THE BAY. EACH OF THE 1048 1B LEAD ANODES IS 3 INCHES IN DIAMETER AND 30 FT LONG, CONTAINING 75 PLATINUM INSERTS 0.0040 INCHES IN DIAMETER AND 1 INCH LONG. THE INSERTS PLACED AT 5 INCH INTERVALS, PENETRATE 0.75 INCH INTO THE LEAD. CURRENT TO THE ANODES AT 24 V DC, FEEDS FROM A RECTIFIER LOCATED IN THE RAIL TUBE. NEGATIVE TERMINALS OF THE ANODES CONNECT TO THE STEEL TUBE. CURRENT FROM THE PLATINUM AUGMENTED LEAD ANODES CANCELS OR NEUTRALIZES LOCAL CORROSIVE CURRENTS ACTING ON THE STEEL RAIL TUBE. THE TUBE ITSELF BECOMES A CATHODE WHOSE FUNCTION IS SIMILAR TO THAT OF THE POLE OF A LARGE BATTERY. OTHER USES OF LEAD-PLATINUM BI-ELECTRODES ARE MENTIONED.
- Publication Date: 1974-3
Media Info
- Pagination: p. 41
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Serial:
- Materials Protection and Performance
- Volume: 13
- Issue Number: 3
- Publisher: National Association of Corrosion Engineers
Subject/Index Terms
- TRT Terms: Anodes; Cathodes; Electrodes; Lead (Metal); Platinum; Protection; Tubing
- Identifier Terms: San Francisco Bay Area Rapid Transit District
- Subject Areas: Geotechnology; Highways; Materials; Security and Emergencies;
Filing Info
- Accession Number: 00217392
- Record Type: Publication
- Files: TRIS
- Created Date: Apr 27 1981 12:00AM