Materials like iron and its alloys (mild steel, stainless steel) are subject of longstanding technological interest for engineering applications due to many advantages. However, one of the major drawbacks is a complex anodic dissolution of iron in contact with an environment containing ionically conducting species which depends greatly upon composition and pH of the electrolyte solution, surface charge (acid-base properties of the surface), etc. The successful application of iron and its alloys relies on the formation of a surface passive layer that significantly modifies the reactivity and represents a key factor of iron protection against corrosion. The environmental restrictions put in focus the use of natural products as green corrosion inhibitors. One of four phenolic acids in natural products, propolis, which is known to possess anticorrosion efficacy for different metals and alloys, is p-coumaric acid. The aim of the present study is to investigate the influence of cinnamic acid derivative (o-coumaric acid (OKA) and p-coumaric acid (PKA)) films on the corrosion resistance of iron in sodium chloride solution by means of dc and ac electrochemical methods. The surface films were characterized using Fourier transform infrared spectroscopy and optical microscopy.