This book contains comprehensive, readable discussions on corrosion reactions and corrosion products, chemical thermodynamics of corrosion, electrolytic mechanism of corrosion, kinetics of electrode reactions, inhibitors of acid corrosion, special aspects of the corrosion of alloys, passivity of metals, pitting corrosion, stress corrosion cracking, and corrosion fatigue.
In previous years, we have explored the use of electrochemical sensors for humidity and corrosion measurements inside of natural gas pipelines. Designed to operate in systems where a conductive aqueous phase is intermittent or unavailable, these membrane-based sensors utilize electrochemical techniques such as linear polarization resistance and electrochemical impedance spectroscopy to determine the environment’s corrosivity to the pipeline material. We now aim to explore this sensor’s performance and capabilities in more complex systems, specifically in environments that promote localized corrosion. Using the aforementioned electrochemical techniques, along with electrochemical noise and cyclic voltammetry, we probe and monitor localized corrosion and general corrosion of X65 steel in the presence of inorganic pitting agents. Experiments are conducted in both aqueous and nonaqueous environments. The additional functionality increases the quantity and quality of corrosion data from these sensors, offering to internal corrosion-monitoring programs a more complete picture of real-time corrosion within their natural gas pipelines.
Stabilized austenitic stainless steel (SS) grade 347 is used extensively in high-temperature processes in the petroleum refining industry, while duplex SS (DSS) grade 2205 is a relatively newer material in the industry. Though these grades of SSs perform well in refinery process streams, there are incidents of failure of process equipment attributable to stress corrosion cracking (SCC). The paper deals with a study on the cracking susceptibility of SS grade 347 and DSS grade 2205 in refinery simulated process environments containing hydrogen sulfide and chloride. The paper also reports the electrochemical behavior of these SSs in the medium containing hydrogen sulfide and chloride. The electrochemical behavior of the alloys was assessed by cyclic polarization experiments. Slow strain rate test (SSRT) was used to evaluate the susceptibility of the alloys to SCC. The cyclic polarization studies indicate that the H2S – chloride synergism had a pronounced effect on the localized corrosion susceptibility of 347 SS, while the effect was marginal on the alloy DSS 2205. The SCC susceptibility of 347 SS and DSS 2205 is strongly influenced by hydrogen sulfide-chloride synergism. Initiation of corrosion pits and the sulfidation of active pits due to the synergism were the important steps in the initiation of SCC.