A Method of Measuring Rates of Corrosion of Iron in the Presence of Carbon Dioxide and Air and the Influence of Electrical Potentials on Such Rates

The method consists in subjecting cylindrical samples of 4ft. by 1/10 ft. wrought iron to the action of water saturated with the gas mixture. The water and gas are passed through the cell at such a rate as to insure a constant and known composition. A precision of 5% is obtained in runs of 48 hours duration. 4% CO2 mixed with air dissolves 1 gram of iron per square centimeter of exposed surface in 735 days while it required 1927 days with air alone. A fall of 25/100 millivolt per centimeter increased the rate of corrosion 28%. 25/1000 millivolt per centimeter had no appreciable effect upon the rate. The conclusion is reached that a fall of more than 25/100 millivolt is necessary. Methods of eliminating corrosion of this type are given