Evaluation of transit stray current interference by optical interferometry methods

It is well known that a metal solid in an electrolyte solution would develop an electrochemical potential difference a cross the interface between the solid and the solution. the electrochemical potential is normally called the open circuit potential (ocp). as a result,exchange currents,cathodic (ic) and anodic (la) currents,will form due to chemical reversible reactions between tlie metal solid and the solution,. the chemical reactions can be either cathodic or anodic reaction. if the cathodic exchange current (ic) is more than the anodic exchange current (la),therefore,a net exchange current would form toward the cathodic polarization of the solid in the solution. this is also a true case during the cathodic protection of the solid in the solution. an excess of cathodic current on the solid metal might lead to the phenomenon of stray current and subsequently to transit stray current interference. in the present work,an evaluation of a transit stray current of a low carbon steel,pure aluminum,a stainless steel,and a copper-nickel alloy in 1m naoh,1mkc1,1m nacl,1mh2so4 solutions,respectively,was conducted by an optical interferometry technique. a transit stray current was solely detected by the optical interferometry of the pure aluminium sample at the open circuit potential of the sample in 1mkcl solution. an excessive measured value of the corrosion current density,19,625.8×10-6 a/cm2,was determine for the pure aluminium sample in 1mkc1 solution as compared to the rest of the alloys in solutions. in contrast,the average noise of current/time measurements of the galvanic coupling between two similar samples of the pure aluminum in 1mkc1 solution was found to be the lowest,4.22×10-6 μa/cm2 by the zero resistance ammeters,among the rest of the alloys in solutions.