Abstract
Vapor phase corrosion (VCI) inhibitors have superior protection performance compared to nitrogen blanketing systems. Proof of this was seen after monitoring the corrosion rate of steel samples for more than five months (roughly 4,000 hours). Corrosion behavior was evaluated in two different conditions; the first contained 200 ppm chloride solution + 10% corrosion inhibitor addition, the second included 200 ppm chloride solution with a nitrogen blanketing system at 10 psi applied pressure. The exposed samples typical of those found in storage tanks and cross casing pipes were tested using linear polarization resistance (LPR) and electrical resistance (ER) probe techniques in the presence of excessive salt and moisture. Vapor phase corrosion inhibitors demonstrated excellent protection in corrosive environments, even where restricted geometries such as crevices, threads, notches and under-deposits exist. The LPR corrosion rate measured less than 0.06 mpy for samples immersed in VCI solution with no observable corrosion. The immersed and nitrogen blanketed samples, in contrast, showed a 1.68 mpy corrosion rate and samples were covered with a thick red rust. ER probes showed a corrosion rate of 0.18 mpy for VCI treated while the nitrogen blanketed samples showed a 2.12 mpy corrosion rate and probes were heavily corroded.
