**3. Redox reactions in corrosion reactions**

Corrosion is another type of redox reaction; it occurs when a metal comes in contact to a solution or at least moisture; the metal corrodes with evolving of electrons that move to cathodic part of the so‐called localized galvanic cell, and then, cathodic reaction starts with the production of hydrogen gas if the electrolyte is acidic or conversion of water to hydroxide if the electrolyte is neutral or basic. In this case, the intensity of flow of electrons from the anodic part (metal) to cathodic part (electrolyte) is defined as the corrosion current; there may be some microscopic galvanic cells with adjacent distance or some distance apart if the electric current in the galvanic cells is huge and is more than the electrolyte capacity to allow the current to pass, then the opera‐ tion is governed by the movement of electrolyte ions; on the other hand, if the electric current is less than the electrolyte capacity to allow the current to pass, then the operation is governed by activation energy. One of the famous corrosion examples is the iron rust, and in this case, iron is oxidized at the beginning to ferrous ions releasing two electrons, and the reaction will proceed as long as the metal is capable of releasing electrons and electrolytic solution to carry the ions; the corrosion current is increased by increasing the number of oxidized iron atoms, and if there is excess of oxygen in electrolyte, then ferrous ions are oxidized further to ferric ions that can give ferric oxide or ferric carbonate which is the main constituent of the iron rust. Besides iron, most of elements in the periodic table are capable to corrode, and corrosion now has become a global problem that should be controlled if it could not be stopped (according to the second law of thermodynamics); the biggest breakthrough that has been achieved in the corrosion research is the invention of the electrochemical series, a series in which ordering the periodic table ele‐ ments depends on the redox potential, and the most benefit of this is trying not to gather two ele‐ ments of far different reduction potential in one alloy because that is produced in fast corrosion.

#### **4. Redox reactions in combustion reactions**

To start a discussion on this, let us first ask this question, is the combustion reactions is a redox reaction? Answering this, as the oxidation state is changed from 0 in the molecular oxygen to −2 in the species that produce in the reaction, the reaction is a redox in nature; combustion in the form of fire produces flame and a considerable amount of heat, which can make combustion self‐sustaining. In case of burning metals such as mercury, copper, zinc, and so on, the product is the metal oxide; in case of burning organic molecules, the products are carbon dioxide, water, and heat, and the combustion reaction is not as easy as it looks; probably the reaction takes place in a series of more than 10 steps, and hence finding the overall rate of reaction becomes extremely complicated, and the computer softwares are the only logical solution for this. MatLab, Avogadro, Copasi, and Kintecus are some of the most powerful softwares used in this regard.
