YEah Sure... Surely plant extract can reduce and inhibit the further corrosion, a very natural plant exract Tannin or Tanic Acid is a Good corrosion inhibitor, many plant barc have in various extent.
Using natural plant extracts as corrosion inhibitors is a very current trend these days. Natural products such as plant extract, amino acids, proteins, and biopolymers have been reported to be efficient corrosion inhibitors . Please take a look at this article.
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Recent Natural Corrosion Inhibitors for Mild Steel: An Overview
Given that almost anything can inhibit corrosion! The problem with natural sources is cost, availability, etc. This is why you made inhibitors industrially.