What are the common methods for corrosion monitoring?

Regular spot thickness measurements can be carried out, and eddy current testing can also be done by removing sections of the pipeline

There are relevant posts on the forum; please refer to http://bbs.hcbbs.com/thread-212252-1-1.html

I. Corrosion detection methods: A. External corrosion detection: External protection system = insulation layer + cathodic protection. Object of inspection – cathodic protection system. Measurement parameters: A. Pipe/ground potential; detection techniques – Person method, intermittent potential detection method, combined potential testing method, DC voltage gradient method, etc. B. Current within the pipe, detection techniques — current gradient distribution method, segmented pipe current comparison method. B. Internal corrosion detection: A. Magnetic flux leakage method B. Ultrasonic method C. Eddy current testing method. II. Methods for online monitoring of internal corrosion: (1) Physical methods: A. Inspection hole method B. Weight loss hanging piece method C. Resistance probe method D. Hydrogen penetration monitoring method E. Inductive probe method F. Fixed-point thickness measurement method (which is a type of non-destructive testing method). (2) Electrochemical methods: G. Linear polarization method H. Electrochemical noise method. Last edited by brucehan on 2009-2-1 13:22.]

In-situ corrosion monitoring techniques based on electrochemical methods (electrochemical noise, resistive probes, magnetoresistive probes). Corrosion control methods mainly involve process-based anti-corrosion strategies and the development of anti-corrosion materials, while corrosion monitoring is a tool used in the corrosion control process. Its purpose is to detect corrosion phenomena on equipment, understand the corrosion process, assess the effectiveness of corrosion control measures, and quickly and accurately determine the degree of corrosion and any potential risks associated with the equipment, so that appropriate anti-corrosion measures can be formulated. 1. Electrochemical noise: Electrochemical noise (ECN) refers to the phenomenon of random, spontaneous fluctuations in potential or current that occur on the surface of an electrode undergoing corrosion. This noise originates from the electrochemical system itself. It does not originate from noise from control instruments or other external disturbances; therefore, compared to other disturbance testing methods, it can more accurately reflect the properties of the system. There are many causes of ECN; common ones include changes in the local anodic and cathodic reaction activities of the corroding electrode, the breakdown and restoration of the passivation film on the surface of the corroding electrode, changes in the thickness of the diffusion layer, the peeling off of surface films, and the formation of bubbles on the electrode surface. 2. Resistance probe: The corrosion rate is measured using a resistance probe by taking advantage of the fact that, when the length of the probe wire remains constant while its cross-sectional area decreases, its resistance value increases. By measuring this change in resistance, it is possible to determine the change in the diameter of the probe wire, and thus calculate the metal’s corrosion rate. The method involves applying a constant current to the probe wire, measuring the voltage at both ends of the wire, calculating its resistance, determining the diameter of the wire, and thus figuring out the rate of metal corrosion. 3. Magnetoresistive probe: Magnetoresistance testing is a new technique for detecting metal corrosion. Similar to resistive probes, it is also based on the measurement of metal loss. By measuring the change in coil inductance, changes in the dimensions of the metal specimen caused by corrosion or abrasion can be detected sensitively. The main reasons for carrying out corrosion monitoring are as follows: 1) To provide a basis for scientific management and decision-making: During oil refining processes, large amounts of corrosion inhibitors are used to reduce internal corrosion in the processing equipment. However, whether the type and ratio of the added corrosion inhibitor are suitable for this system can only be determined through specific measurements. By using corrosion monitoring, it is possible to continuously assess the effectiveness of the corrosion inhibitor, and to adjust the type or concentration of the inhibitor in a timely manner based on the monitoring results ； 2) Preventing accidents: Harmful leaks or changes in process parameters can sometimes lead to severe corrosion. By using corrosion monitoring, it is possible to keep an eye on the corrosion status of the medium at any time. If a sudden change in the corrosion rate is detected, the system is inspected immediately to identify the problem promptly and prevent serious accidents from occurring ； 3) Predicting equipment lifespan: By monitoring corrosion, it is possible to accurately determine the corrosion rate under normal operating conditions of the equipment, thereby allowing for the prediction of its service life – ensuring both safety and cost-effectiveness ； In addition to bringing significant economic benefits by improving the operating conditions of equipment, enhancing its reliability, extending its service life, and reducing downtime for maintenance, corrosion monitoring technology also enables the installation to operate under conditions as close as possible to those optimal for design. It can also play a positive role in ensuring the safety of the equipment, protecting the operators, and reducing environmental pollution ； Corrosion monitoring is also useful for analyzing the causes of corrosion, understanding the relationship between the corrosion process and process parameters, or evaluating the actual effectiveness of certain anti-corrosion methods. This post was last edited by brucehan on 2009-2-1 13:28]

Our factory uses an online corrosion monitoring system that employs the inductive probe method. It uses the technology from the Shenyang Institute of the Chinese Academy of Sciences. The principle is very simple; it was just installed, and I don’t know how effective it will be.

What are the results of the monitoring? Do they provide practical guidance for corrosion monitoring, and is it easy to apply them in practice?