Evaluation of Iron Corrosion Rate in Solution Containing Inhibitors by Using Coulostatic Method
Yuichi Sato, Tomoyoshi Hamada, Takehiro Owa, Shoichi Sugiyama, Koichi Kobayakawa
In order to expand and clear the applicable range of the coulostatic method to measure the metal corrosion rate in solution, the method was tested by measuring the corrosion rate of iron in water containing three types of inhibitor, i.e., potassium chromate, polyphosphate with calcium ion and sodium nitrate, in stagnant state. Though the potential decay curve did not obey the theoretical equation at the initial stage because of the film formation by the inhibitors, the over-potential ηt at t=0 was obtained by extrapolating the linear parts of the log ηt polts to t=0. The corrosion rates obtained by using ηt and other parameters gave good agreement with those obtained by the weight loss method for the same samples. So, from a practical standpoint, the coulostatic method was found to be applicable for iron corrosion rate monitoring in the solution containing above inhibitors.