Anticorrosion potential of diethylenetriaminepentakis (methylphosphonic) acid on carbon steel in hydrochloric acid solution

• DTMP is good organic corrosion inhibitor for carbon steel in 1 M HCl.
• Weight loss and EIS methods are in reasonable agreement.
• EPMA results showed that the corrosion process is inhibited by the adsorption of DTMP on steel surface.
• DTMP adsorption is well described by Langmuir isotherm.

The inhibition ability of diethylenetriaminepentakis(methylphosphonic) acid (DTMP) against carbon steel corrosion in 1 M HCl at 30 °C was evaluated by weight loss, ac impedance and electron probe microanalyser (EPMA) methods. The experimental results showed that DTMP was a good inhibitor for the steel corrosion in 1 M HCl medium and its inhibition efficiency increased with the inhibitor concentration. Data, obtained from ac impedance measurements, were analysed to model the corrosion inhibition process through appropriate equivalent circuit models. Adsorption of DTMP on the carbon steel surface followed the Langmuir adsorption isotherm. Surface analysis supported the formation of a protective inhibitor film on the carbon steel surface.