Humic acid as eco‐friendly corrosion inhibitor for EH40 ship plate steel

In this study, a new type of green corrosion inhibitor, namely, sodium humate (SH), was extracted from humus soil, which is a natural humus plant, by dissolution‐neutralization, and then used for corrosion inhibition of low carbon steel in seawater. The corrosion inhibition performance of SH on low carbon steel EH40 in seawater was tested by weight loss method and electrochemical technology. The surface and corrosion products of low carbon steel were observed and analyzed by scanning electron microscope (SEM), atomic force microscope (AFM), contact angle and X‐ray photoelectron spectroscopy (XPS). The results show that SH is a mixed corrosion inhibitor, and the optimum concentration is 2 g L −1 . At this concentration, the inhibition rate can reach 93.6%. It mainly affects the semi‐reaction of cathodic corrosion. By forming a corrosion protection layer with uniform adsorption on the surface of EH40 steel, EH40 steel becomes more resistant to seawater corrosion.