Electrochemical screening of organic inhibitors for corrosion of UNS N0400 in saturated monoethanolamine solution

Abstract

In response to environmental concerns associated with the buildup of arsenic sludge used in A. AL-HASHEM the monoethanolamine (MEA) CO 2 removal unit at a refinery in Kuwait, two organic based J. A. CAREW inhibitors have been evaluated as potential replacements for the inorganic sodium arsenate A. HASAN used earlier. T he inhibitors were evaluated for UNS N0400 (Monel 400) in f resh MEA solution saturated with an 85H 2 -15CO 2 gas mixture at 40°C using electrochemical impedance spectroscopy, potentiodynamic polarisation, and weight loss techniques. Interfacial impedance data obtained at low frequencies were marginally higher when the two organic inhibitors were added. T he percentage eYciency obtained by the potentiodynamic method was 66% for an amide based inhibitor and 15% for an amine based inhibitor. Weight loss data also indicated that the corrosion rate of N0400 in the MEA solution with the amide based inhibitor was lower than that with the amine based inhibitor.T he authors are in the

Charge and pH effects on inhibitor performance

“…This was thought to be due to the presence of substituted groups which prevented the inhibitor from lying flat on the steel surface. Similarly it was found that in 18 per cent monoethanolamine solution (saturated with 8 per cent H 2 S, 15 per cent CO 2 ), an amide based inhibitor (66 per cent efficiency), was more effective than an amine type (15 per cent efficiency), in reducing the corrosion rate of UNS400 steel at 40 C (Al-Hashem et al, 1999).…”

Some thoughts about misconceptions surrounding the term ‘biofilm'

“…Perhaps one of the most important features of biofilms is that under-biofilm conditions could be far different from the bulk solution in almost all respects; for instance, by typically reaching a thickness of 12 micrometres, the under-biofilm environment will become anaerobic (oxygen-free) [7]. In fact, under-biofilm factors such as pH, dissolved oxygen, etc.…”