Green approach in anti-corrosion coating by using Andrographis paniculata leaves extract as additives of stainless steel 316L in seawater

Abstract

The analysis of anticorrosion coating by using Andrographis paniculata (kalmegh) leaves extract (KLE) as an additive to protect stainless steel 316L that immersed in seawater environment was successfully carried out. The anti-corrosive coating is the combination of selected binder, pigment, solvent, and additive. Andrographis paniculata leaves extract was selected as an additive due to excellent antioxidant properties. There are five types of coating with different concentration which are C1 (0 wt.%), C2 (3 wt.%), C3 (6 wt.%), C4 (9 wt.%) and C5 (12 wt.%). The coated substrate the immersed in seawater for 30 days and taken out for each subsequent 10 days for analysis. The analysis involves optical, electrochemical, and morphology studies. A few techniques involve including of Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM/EDS). The result of FTIR shows several functional group presence in the KLE that can enhance anti-oxidation properties such as phenol, carboxylic acid, carbonyl, and amide. The presence of andrographolide compound obtained from UV-vis analysis at peak absorption spectrum 229 nm. Electrochemical analysis result from EIS, the most efficiency coating was predicted at C3. Hence, it has higher Rct value and low Cdl value. The result in EIS is corresponding to PP; hence the result of corrosion rate at C3 is the lowest value, which is 0.00211 mm/year at 30th day immersion. The observation on the surface morphology of the coating also shows that C3 that has a smooth surface with less pitting, cracks, and salt precipitate when compared to another coating. The addition of KLE increases the efficiency of anticorrosion coating with optimum concentration, which is 6 wt.%.