Corrosion
- What is corrosion and why is it called the reverse of metal extraction? In one line Corrosion is the gradual destruction or deterioration of a metal by chemical or electrochemical reaction with its environment, s... 1
- How does dry or atmospheric corrosion occur, and what decides whether the oxide film protects the metal? In one line Dry corrosion is direct chemical attack of a metal by dry gases (mainly oxygen) forming a surface film, and the nature of this f... 1
- What is the hydrogen evolution mechanism of wet corrosion in an acidic medium? In one line In an acidic, oxygen-poor environment, the metal dissolves at anodic areas and the released electrons reduce H⁺ ions to hydrogen... 1
- How does iron rust in neutral water by the oxygen absorption mechanism? In one line In a neutral or slightly alkaline medium containing dissolved oxygen, iron is oxidised at anodic areas while oxygen is reduced t... 1
- How do selection of metal and proper design help prevent corrosion in engineering structures? In one line Choosing the right (noble or corrosion-resistant) metal for the environment and designing parts so that moisture, crevices and d... 1
- How do the galvanic series position, metal purity and nature of corrosion product affect corrosion rate? In one line Corrosion is faster when the metal is more active (higher in the galvanic series) or coupled with a very different metal, when i... 1
- How do temperature, pH, concentration and moisture of the medium change the rate of corrosion? In one line Corrosion generally speeds up with higher temperature, lower pH (more acidic), higher concentration of corrosive ions and higher... 1
- Why does a small anode with a large cathode corrode so fast, and how does overvoltage affect corrosion? In one line Corrosion is intense when the anodic area is small compared with the cathodic area, and it is slower when the hydrogen overvolta... 1
- What is cathodic protection, and how do sacrificial anode and impressed current methods work? In one line Cathodic protection prevents corrosion by forcing the whole metal structure to act as the cathode, using either a more active sa... 1
- How do anodic and cathodic corrosion inhibitors slow down corrosion? In one line Corrosion inhibitors are substances added in small amounts to the corrosive medium that reduce the rate of corrosion by blocking... 1
- What is the difference between galvanising and tinning as anodic and cathodic metallic coatings? In one line Galvanising coats iron with a more active metal (zinc), giving an anodic coating that protects even when scratched, while tinnin... 1
- Why do electronic devices and circuit boards corrode, and how is it prevented? In one line Electronic devices corrode because tiny metal tracks, solder joints and connectors are exposed to moisture, ionic contamination... 1
- How material selection and proper design of equipments can prevent corrosion. Explain with the help of diagram and designing principles. 1. Proper selection of material Use noble or corrosion-resistant metals (Pt, Au, Ti) or alloys such as stainless steel and cupronickel where... 1
- Distinguish between galvanizing and tinning. GalvanizingTinning Iron or steel is coated with zinc, usually by dipping in molten Zn at about 450 °C.Iron or steel is coated with tin, usua... 1
- How do following factors affects the rate of corrosion i) PH medium ii) Purity of metal iii) Area of anode and cathode. i) pH of the medium: the rate of corrosion generally rises as pH falls, because acidic media supply H⁺ for the cathodic reaction (2H⁺ + 2e⁻... 1
- Explain the sacrificial anode cathodic protection method with a neat and well-labelled diagram. Cathodic protection: the metal to be protected is forced to act as the cathode of an electrochemical cell, so it does not corrode. Corrosion... 1
- How can material selection and design prevent corrosion? Explain which protective coatings can be used for corrosion prevention. 1. Proper selection of material Use noble or corrosion-resistant metals (Pt, Au, Ti) or alloys such as stainless steel and cupronickel where... 1
- Explain the rusting of iron with the help of the electrochemical theory of corrosion and a diagram. Electrochemical (wet) theory: when a metal is in contact with moisture or an electrolyte, many tiny galvanic cells form on its surface. The... 1
- What is cathodic protection? How is it done by using impressed current and sacrificial anode? Explain with suitable examples. Cathodic protection: the metal to be protected is forced to act as the cathode of an electrochemical cell, so it does not corrode. Corrosion... 1
- Explain the effect of following factors on the rate of corrosion : (1) Nature of corrosion product. (2) pH (3) Anodic and cathodic areas (4) purity of metal (1) Nature of the corrosion product (oxide film): in dry corrosion the oxide layer formed on the surface decides further attack. Stable, non... 1
- Define corrosion, how you will join the metals to prevent corrosion, justify with diagram. Corrosion is the gradual destruction or deterioration of a metal by chemical or electrochemical attack from its environment, starting at the... 1