This article proposed a new electrochemical direct measurement method for the evaluation of the rust preventing ability of metal/rust preventive oils using wire beam electrode. Based on a large number of test comparisons with ISO humidity cabinet and salt spray tests, this method has been proven to be effective and accurate. The measurement is ten folds to several hundred times faster than ISO humidity cabinet and salt spray tests. The test equipment is small, portable and especially useful in shortening the time for new product development, in-situ inspection and energy conservation.