Cleaning and Corrosion Control Vol. I CH. 1

Question 1

What is Corrosion?

Answer 1

Corrosion is the electrochemical deterioration of a material or its properties due to its chemical reaction with the surrounding environment.

Question 2

What is an Atom?

Answer 2

The smallest unit of an element, made up of a positively charged nucleus surrounded by a system of negatively charged electrons.

Question 3

What is an Electron?

Answer 3

A negatively charged subatomic particle.

Question 4

What is an Ion?

Answer 4

An atom or group of atoms or molecules which has acquired a net electric charge by gaining (negative ion) or losing (positive ion) electrons.

Question 5

What is an Electrolyte?

Answer 5

A liquid (usually water) solution containing ions.

Question 6

What is Electrochemistry?

Answer 6

The branch of science concerned with chemical reactions at surfaces in contact with electrolytes.

Question 7

What FOUR conditions must be present for corrosion to occur?

Answer 7

• A metal which has the tendency to corrode (Anode)
• A dissimilar conductive material (Cathode)
• A conductive liquid (Electrolyte)
• Electrical contact between Anode and Cathode

Question 8

What are some factors that enable the development of corrosion?

Answer 8

• Biological Organisms
• Mechanical Stress
• Length of Exposure

Question 9

What is Galvanic Corrosion?

Answer 9

The corrosion that occurs when two different metals are in contact with each other and an electrolyte (water).

Question 10

What is Pitting Corrosion?

Answer 10

Extremely localized attack that results in holes in the metal.

Question 11

What is Intergranular Corrosion?

Answer 11

An attack on the grain boundaries of the metal.

Question 12

What is Exfoliation Corrosion?

Answer 12

An advanced form of Intergranular Corrosion where the surface grains of a metal are lifted up by the force of expanding corrosion products occurring at the grain boundaries.

Question 13

What is Crevice Corrosion?

Answer 13

One of the most familiar types of corrosion. It occurs in any crevice where stagnant solution has pooled.

Question 14

What is Filiform Corrosion?

Answer 14

A form of Crevice Corrosion that occurs on metal surfaces having a thin organic protective coating. It contains wormlike traces of corrosion and does not weaken or destroy the base metal. Most prevalent in humid environments.

Question 15

What is Erosion Corrosion?

Answer 15

Erosion due to impingement or cavitation that is characterized by grooves, gullies, wakes, rounded holes, and/or valleys in the metal surface.

Question 16

What is Stress Corrosion Cracking?

Answer 16

Cracking of metals caused by the combined effects of constant tensile stress and corrosion.

Question 17

What is Hydrogen Embrittlement?

Answer 17

Caused by penetration of Hydrogen into a metal, resulting in loss of ductility and tensile strength.

Question 18

What is Corrosion Fatigue?

Answer 18

The cracking of metals caused by the combined effects of cyclic stress and corrosion.

Question 19

What is Fretting Corrosion?

Answer 19

Occurs at contact areas between materials under load subject to repeated vibration.

Question 20

What is Hot Corrosion (High Temperature Oxidation)?

Answer 20

Corrosion that occurs at high temperatures such as turbine engines and afterburners. When hot enough metals can react directly with the surrounding gases, producing oxide scale.