Effective corrosion inhibitor of mild steel in marine environments: Synthesis and application of hydrazides

A new corrosion inhibitor of long chain fatty hydrazides (HH) were synthesized from hydrazine hydrate and natural grease. The current research aimed to examine the effectiveness of HH as a mild steel corrosion inhibitor in maritime applications. The corrosion inhibition experiments were conducted in a saturated calcium hydroxide solution containing 3.0% NaCl. Measurements of weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods were used to assess corrosion inhibition. The molecular structure of HH was analyzed through FTIR and NMR, providing a description. Furthermore, the examination included the effects of concentration, temperature, and time on inhibition. The weightlessness results show that the corrosion inhibition rate of HH-1 is about 70% at low concentration of 10 mg·L−1, further corrosion inhibition rate reaches to about 80% at 20 mg·L−1, and inhibiting rate reaches higher than 90% at 50 mg·L−1 in 3.0% NaCl-containing saturated Ca(OH)2. Polarization test results demonstrated that HH-1 was a cathode-based corrosion inhibitor, slowing down the dissolution of steel by blocking the active site on metal surface. What's more, the adsorption on the mild steel followed Langmuir adsorption isotherm model, 3D scanning, AFM and XPS characterization demonstrated the formation of a protective layer on the steel surface as a result of adsorption of functionalized HH molecules. This layer effectively shielded the steel from aggressive 3.0% NaCl attack following a 48-h immersion in the solution. Quantum chemical calculations and molecular dynamics simulations provided insights into the molecular/atomic-level inhibition mechanism. Ultimately, our research findings validate the effectiveness of a novel environmentally friendly and efficient corrosion inhibitor in safeguarding steel bars against corrosion in marine environments.