Combined experimental and computational studies on corrosion inhibition of Houttuynia cordata leaf extract for steel in HCl medium

The development of corrosion inhibitors that could spontaneously adsorb immediately on the metal surfaces after they are damaged by electrochemical reactions would remarkably arise the improvement of cost-saving, durability and environmental impact of metals. The use of leaf materials for metal corrosion remains an important challenge due to the high corrosion protection, availability as natural materials, environmental friendly and low-cost. Herein, we report a Houttuynia cordata leaf extract as a green corrosion inhibitor that acts as a mixed type of inhibitor for steel in an aqueous 0.1 M hydrochloric acid solution. It also performs the high inhibition performance (up to 98.3% by adding 1500 ppm inhibitor), spontaneous uniform and smooth film formation of the steel surface and less corrosion attack when the H. cordata leaf extract is added to the aqueous hydrochloric acid solution. In contrast to the inhibited systems, uninhibited specimen is severely corroded at high corrosion rate, which is associated with a significant degradation of the entire steel surface. Additionally, investigation on good adhesion and thermal stability of the protective film, as well as enriched electron abundance of selected inhibitor species are performed via molecular dynamics simulation method. Furthermore, insights of corrosion, inhibition and spontaneous film formation mechanisms are also proposed and discussed in detail.