Experimental and numerical studies of surface contamination and degradation of aluminium contacts in primary aluminium smelters

Primary aluminium smelters utilise many high amperage direct current (DC) electrical contacts. They can be subject to extreme modes of degradation, resulting in high contact resistances and significant unwanted power consumption. It is common that stray alumina is present on the top of the anode beam behind the anode rod and can enter the anode beam to anode rod contact. Alumina in the contact causes physical separation of the two contact surfaces resulting in high joint voltage drop readings in excess of 50 mV. Further, anode rods with raised defects due to arcing damage will prevent the remainder of the anode rod surface from properly contacting the anode beam, thus significantly increasing the contact resistance These damaged rods must be removed from the rodding circuit. Electrical contact resistance values for each of the degradation scenarios mentioned above were experimentally obtained. Accompanying computer modeling studies were seen to add insights to experimentation and showed promise towards helping develop optimum economic criteria for the repair and correction of anode rod contact face.