Testing and Corrosion Study by Harco Corporation Huntington
Beach, CA

1. INTRODUCTION
   The testing and corrosive study of the MG Coupling was preformed in July, August, and September of 1976. The primary purpose of the testing and corrosive study was to determine the effectiveness of the bi-metallic galvanic cell between the stainless nuts and bolts and the cast-iron coupling body.
   
   1. Dissimilar metal/Bi-Metallic Cells:
      The simplest cell to visualize is a bi-metallic cell. Such a cell can be established whenever different metals are used as long as there is electrical contact between them provided they are in a common electrolyte (soil or water). Under such conditions, any two dissimilar metals may be expected to have an electrical potential between them. The determining factor of which metal becomes anodic or cathodic depends on its relative position in the electromotive series.
   
   

2. TEST PROCEDURES:
   
   1. Test Set Up:
      The MG Couplings were tested in a corrosive environment by means of submerging couplings in both fresh and synthetic seawater.
      

      The couplings were disassembled and copper wires were attached to the coupling halves by means of thermite welding and also to the stainless steel bolts units by means of brazing. The coupling halves and bolts units were then placed into their respective bins of fresh and synthetic seawater.
      

      Complete coupling units were also put under test in the synthetic seawater bin and in the fresh water bin.
      
      

   2. Structure-to-Water Potentials:
      Each metal has its own potential in the electromotive series. Stainless, which is lower on the series, and cast-iron which is higher create a bi-metallic cell when placed in a common electrolyte. Thus, when they are placed in different resistivity electrolytes, the different effect will be varying potentials.
      

      Structure-to-water potentials were taken and recorded on the stainless steel nuts and bolts. All potentials were obtained using the Miller Multi-Combination Meter Model M3M-A and a copper-copper sulfate half cell as a reference electrode.