Electromotive Series and Reduction Potential
Factors in Bi-Metalic Corrosion
The greater the numerical difference between metals the greater the electrical potential. In a corrosion situation with an electrolyte metals tend to disolve and try to plate metals lower on the chart.
The 1898 chart is given as a reference but does not reflect modern science.

1898 Tables and Formulas, The Colliery Engineer Co., p.69 The Electromotive Series
Marks’ Mechanical Engineers Handbook, 6th Ed., 6-122, Electromotive Force Series in Metals
ASM Metals Reference Book, 2nd Ed. p.98 Reduction Potential
Copyright (c) 2001 Jock Dempsey, anvilfire.com