The addition of inhibitors significantly reduces the rate of corrosion on a metal surface. Inhibitors are chemicals that, when added to a corrosive environment, decrease the corrosion rate of a metal. They function by forming a protective film on the metal surface, blocking the electrochemical reactions that cause corrosion, or by altering the corrosive environment itself. There are two main types of inhibitors: anodic and cathodic inhibitors.Anodic inhibitors work by forming a passive film on the metal surface, which acts as a barrier to the corrosive environment. This film is usually an oxide or a complex compound of the metal ions. The inhibitors react with the metal ions produced during the anodic reaction oxidation and form a stable, insoluble compound that adheres to the metal surface. This protective layer prevents further dissolution of the metal and reduces the rate of corrosion.Cathodic inhibitors, on the other hand, slow down the cathodic reaction reduction by either adsorbing onto the metal surface or reacting with the products of the cathodic reaction. They can also precipitate on the metal surface, forming a barrier that prevents the corrosive species from reaching the metal. This reduces the rate of the cathodic reaction and, consequently, the overall corrosion rate.Some inhibitors, known as mixed inhibitors, have both anodic and cathodic inhibiting properties.The specific molecular interactions that contribute to the inhibiting effect include:1. Adsorption: Inhibitor molecules adsorb onto the metal surface, forming a protective film that prevents the corrosive species from reaching the metal. This adsorption can be either physisorption physical adsorption or chemisorption chemical adsorption , depending on the strength of the interaction between the inhibitor and the metal surface.2. Formation of a passive film: Inhibitors can react with the metal ions produced during the anodic reaction to form a stable, insoluble compound that adheres to the metal surface, creating a barrier against further corrosion.3. Complexation: Some inhibitors form complexes with the metal ions in the corrosive environment, reducing the concentration of the free metal ions and slowing down the corrosion process.4. Altering the corrosive environment: Inhibitors can also change the properties of the corrosive environment, such as pH or the concentration of corrosive species, which can reduce the corrosion rate.In summary, the addition of inhibitors affects the rate of corrosion on a metal surface by forming a protective film, blocking electrochemical reactions, or altering the corrosive environment. The specific molecular interactions that contribute to this effect include adsorption, formation of a passive film, complexation, and altering the corrosive environment.