Electrochemical insights on silicate-based corrosion inhibition for pipeline materials

In many industries, using corrosion inhibitors to protect piping systems remains a highly cost-effective strategy. While the primary goal is to reduce corrosion to acceptable levels, there is a growing demand for sustainable, "green" alternatives. Sodium silicate (SS) has emerged as a promising candidate, offering a non-toxic, eco-friendly, and readily available inorganic solution.

This study evaluates SS as a corrosion inhibitor for steel, copper, and zinc in flowing saltwater. To simulate the conditions of an open recirculating cooling water system, a rotating-cylinder electrode setup was used, with surface flow speeds ranging from 0.5 to 1 m/s. A comprehensive electrochemical evaluation was performed using potentiodynamic scans (PDS), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (M-S) analysis.

The results from PDS and EIS demonstrated that SS drastically lowers corrosion rates by forming protective layers. Inhibition efficiencies reached up to 99% for steel, 97% for copper, and 88% for zinc. EIS and M-S curves provided additional insights into film structure, revealing a direct link between improved film properties and overall film stability. However, the interaction with zinc proved complex; at low concentrations, a competition emerged between the formation of the protective silicate layer and the development of non-protective insoluble species.

The study also highlighted a distinct difference in flow speed interaction for each metal. Combined EIS and M-S analysis revealed an interesting interplay between SS concentration and flow velocity. The resistance to flow-induced degradation varied significantly with substrate material and inhibitor bulk concentration. Ultimately, these findings confirm that sodium silicate is a highly effective and versatile green alternative for protecting multi-metal piping systems under dynamic flow conditions.