Sulfuric acid is one of the most important elementary substances of the chemical industry. There is no stainless steel or even a nickel base alloy available which is suitable over the entire concentration range. This paper will give corrosion data in up to 75 % sulfuric acid at boiling temperature for various commercial grades as well as for some new developmental alloys.
Under-deposit corrosion is a common mode of failure in boiler tubes. Mechanisms include phosphate attack, caustic gouging, hydrogen damage, and wall thinning due to metal loss. Many aspects of these mechanisms and their mitigation are well-understood, while certain specific details remain uncertain or subject to controversy.
If the iron concentration in an alkaline chelant boiler cleaning solution reaches a high value when dissolving magnetite, it sometimes continues to increase rapidly and not level, indicating corrosion of the boiler metal. A laboratory study of “runaway iron increases” investigated the cause and the best mitigation methods.