Evaluating the performance of andrographis paniculata leaves extract as additive for corrosion protection of stainless steel 316l in seawater

Abstract

Anti-corrosion protection coating serves as an effective way for the reduction of corrosion progress in a corrosive environment. With the increase of interest in green corrosion protection nowadays, Kalmegh or Andrographis paniculata from the family of Acanthaceae is evaluated for its potential as an additive in coating for stainless steel grade 316L (SS316L) via electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and scanning electron microscope (SEM) in seawater. Characterization via Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-Visible (UV-Vis) spectroscopy and High Performance Liquid Chromatography (HPLC) revealed the presence of asymmetry –NH, –CH and –OH, two peaks at 450 nm and 661 nm as well as the identification of andrographolide with a retention time of 4.650 min. Results showed an increase in corrosion resistance as the extract concentration in the coating increase. However, the efficiency was found to be limited at 10% extract concentration, and further increase diminished its inhibitive effect. Base on electrochemical analysis, coatings with the additive exhibited a mixed-type inhibitive property which was identified through the polarization curve. SEM micrograph of the coated steel surface showed inhomogeneous layers with rough structure possibly due to an aggressive attack of corrosive species in the medium on multiple sites.