A process for ascertaining the degree of the absolute or relative resistance to rusting shown by iron, steel and iron alloys

摘要

292,794. Mauler, C. July 28, 1927. Testing, - A process for ascertaining the resistance of iron, steel &c. to rusting, used in the manufacture of rustless steels, consists in immersing the specimens in an alkaline oxidizing solution, which is kept in a boiling condition and noting the temperature at which the first signs of corrosion appear, the temperature having a definite relation to the concentration of the liquid. It has been found that steels which require a high concentration of the boiling liquid are those which exhibit the greatest degree of resistance to rusting. Conveniently, the specimens are removed from the liquid and examined at each degree of increase in the boiling point. The solution consists of an alkali, such as caustic soda or potash, and an oxidizing agent, such as a nitrate, permanganate, bichromate, peroxide or an aromatic nitro compound. To this solution is added some of the solution left from a previous test and containing the solid reaction products. In an example, 60 to 70 kilogrammes of caustic soda are dissolved in 20 to 40 litres of water together with 8 to 15 kilogrammes of sodium nitrate, 1 to 3 litres of the reaction products referred to above and, to maintain the alkalinity constant, 1 kilogramme of slaked lime for every 100 litres of the solution, the boiling point of which is approximately 1400 C.