Galvanic Corrosion of Structural Aluminum Coupled with Mild Steel in a Dilute Sodium Dichromate Electrolyte

摘要

The study was concerned with the corrosion rate of aluminum coupled with, and insulated from, a large mild-steel cathode in five different solutions including seawater, tap water, distilled water, and two inhibitor solutions. Aluminum cathodically protects steel when large cathode-to-anode area ratios exist. The corrosion rate of the aluminum anode may be reduced by more than two orders of magnitude by disconnecting the couple. The presence of an inhibitor increases the corrosion rate of the uncoupled aluminum by about 35 percent, but this disadvantage is more than offset by the reduced corrosion of the steel cathode, making the use of an inhibitor highly desirable. It was found that the corrosion rate of the aluminum anode of the aluminum-steel couple had two components, a galvanic component which is a function of the galvanic current flow and a local component to which all other weight loss is attributed. For uncoupled specimens the galvanic component does not exist, and the local component is reduced by more than one order of magnitude. (Author)