Acid Inhibitors, commonly known as Acid Corrosion Inhibitors, are products that have been specially designed to provide protection to base metals against corrosive actions of strong acidic substances.
What is corrosion?
Corrosion can essentially be defined as an electrochemical process. Any ferrous metal comprises of iron, different alloying elements (manganese, sulfur, copper, phosphorous, carbon, nickel, silicon, chromium, aluminum), and impurities such as phosphides, sulphides, etc.
How corrosion occurs?
There is a definite electro-potential difference between any two constituents of steel. In an acid solution, this potential difference within the metal induces a flow of electrons to a developing cathode on the metal surface, with the formation of anodes where the me`tal gets dissolved.
At the cathode, hydrogen is evolved from the alleviation of hydrogen ions. After the acid dissolves the oxides and other deposits, the acid completes the circuit on the metal surface. Hydrogen is evolved and metal gets dissolved.
Now, let us understand why metals get corroded!
Mild steel is used extensively as the constructional material in many industries owing to its excellent mechanical characteristics and modest cost. Acidic solutions are extensively used in various industrial processes, some of the critical fields of application being acid pickling of steel, ore production and oil well acidification, chemical cleaning and processing, etc.
Importance of using Acid Inhibitor
Owing to the high corrosive nature of acids, these metals tend to get corroded when subjected to acidic cleaning or scale removing applications. This brings the acid inhibitors or acid corrosion inhibitors to play. These inhibitors are used to alleviate the corrosive attack on metallic elements. Though the selection of these inhibitors depend mainly upon three features–
a) Its efficiency to inhibit the substrate material
b) Its economic availability
c) Its environmental side effects
Most of the excellent acid inhibitors for corrosion of steel in acidic medium are organic compound containing nitrogen, oxygen and/or sulphur atoms.