Carbon steel is the most common pipe material used in the hydrocarbon processing industry, but the material’s susceptibility to corrosion is well known. Sulfidic corrosion of piping and equipment continues to be a significant cause of leaks and issues that can lead to early replacements, unplanned outages, and incidents potentially resulting in loss of property and injury to workers.
Corrosion can be caused by impurities in the steel pipe, or by impurities in the oil. Analyzing Metals has published many posts evaluating steel pipe corrosion resulting from faulty steel. Carbon steels with low-silicon content can corrode at an accelerated rate when exposed to hydrogen-free sulfidation corrosion conditions. According to the American Petroleum Institute (API) Recommended Practice 939-C (Guidelines for Avoiding Sulfidation Corrosion Failures in Oil Refineries), one-third of high temperature sulfidic corrosion failures are the result of low silicon content. Hydrogen-free sulfidation can occur in crude/vacuum equipment and fluid catalytic cracker, coker, and visbreaker units. Hydroprocessing and hydrocracking units can experience hydrogen-free sulfidation corrosion in their feed and distillation sections. To help prevent these incidents from occurring, silicon analysis of such piping and equipment with portable X-ray fluorescence (XRF) is currently one of the best solutions to verify the composition of piping, valves, and reaction vessels. Read Analysis of silicon in steel using the Thermo Scientific Niton XL5 analyzer to prevent sulfidic corrosion failures to for study results demonstrating that an XRF analyzer is able to reliably detect Si levels in steel at less than 0.05%.
Even when steel piping is manufactured to the appropriate specifications for hydrocarbon processing, impurities in the crude oil itself can cause corrosion in pipelines and refinery equipment. MIT Technology Review reports on a company that is working in collaboration with oil companies to address this issue with a new process to increase steel strength by as much as 10 times, and make it more corrosion-resistant. If the modified metals pass field testing, the new process could not only make steel piping and equipment last much longer, but also bridges and other infrastructure, and make cars lighter and therefore more fuel-efficient.
According to the article, the process involves an advanced form of electroplating using a bath that contains more than one kind of metal ion and controls how ions are deposited by varying the electrical current. By changing the current at precise moments, it can create a layered structure, with each layer being several nanometers thick and of different composition. The final coating can be up to a centimeter thick and can greatly change the properties of the original material.
We recently reported on another idea to address the pipe corrosion issue: plastic pipes. Read Is Plastic Pipe The Answer to Combating Corrosive Steel in Hydrocarbon Processing? to learn why plastic pipe material has been investigated as an economical and corrosion-resistant alternative to steel pipe.