Chapter 2 - Corrosion

Question 0

What is passivation?

Answer 0

A layer of oxides formed on the surface of a metal that provides corrosion protection. Stainless steel for example.

Question 1

Define corrosion.

Answer 1

The deterioration of a substance, usually a metal from a reaction with its environment.

Question 2

What are the elements of a corrosion cell?

Answer 2

Anode
Cathode
Metallic Pathway
Electrolyte

Question 3

Describe what happens at the anode.

Answer 3

The metal dissolves into the electrolyte.

Question 4

What is the function of the electrolyte?

Answer 4

Allows the passage of ions to connect the corrosion cell.

Question 5

What is the function of the metallic pathway?

Answer 5

Allows the flow of electrons to connect the corrosion cell.

Question 6

What is the galvanic series?

Answer 6

A listing of metals in order of reactivity (more or less noble) in seawater at 25*C.

Question 7

The general rules of galvanic corrosion are:

Answer 7

The less noble (or more reactive) metal when connected to a more noble (or less reactive metal) will corrode preferentially.

Question 8

Name the five most important factors that affect the rate of corrosion temperature.

Answer 8

Humidity
Oxygen
Chemical salts
Pollutants
Gases

Question 9

General corrosion is:

Answer 9

• Results in a relatively uniform loss of material over the entire surface
• Results in a general thinning of the affected surface
• Relatively easy to inspect
• Does not cause catastrophic failures

Question 10

Localized corrosion is:

Answer 10

Typically Pitting and Crevice Corrosion. It is typically of the most concern as damage is concentrated and loss of integrity or structural failure can result.

Question 11

List some of the common tools/methods used for corrosion control.

Answer 11

• Design
• Inhibitors
• Material Selection
• Cathodic Protection
• Protective Coatings
• Splash Zone Systems
• Alteration of the Environment