Corrosion - 1

Question 1

Corrosion can be generally defined as degradation of a metal by ,,,,,,,,, or ,,,,,,,,, means

Answer 1

chemical or electromechanical

Question 2

Two mechanisms are involved in corrosion, firstly ,,,,, and secondly ,,,,,,,,.

Answer 2

An electrical circuit & Chemical reaction.

Question 3

In a corrosion circuit the current is always ,,,,,

Answer 3

direct current (DC).

Question 4

It is conventionally thought that a current passes from ,,,,,, to ,,,,,,, but electrons are flowing the opposite direction, ,,,,,,

Answer 4

• positive + to negative
  (anode to cathode)
  -from cathode to anode

Question 5

For a corrosion circuit to exist three things are needed

Answer 5

• Anode
• Cathode
• Electrolyte

Question 6

An anode is a ,,,,,, charged area which becomes positively charged because the atoms ,,,,,, two electrons each

Answer 6

positively
release

Question 7

Anode:
In its ,,,,,, state, the iron atom has 26 of each, protons and electrons

Answer 7

passive

Question 8

Anode:
when the two ,,,,,, are released, the atom still has its 26 ,,,,,,, but only ,,,,,,, . In this state the atom is now ,,,,,

Answer 8

electrons
protons
24 electrons
an ion

Question 9

Anode:
overall positively charged iron by two units and written as ,,,

Answer 9

Fe++

Question 10

An ,,,,,, is a charged particle and can be
positive or negative, a single or a group of atoms, known as a molecule

Answer 10

ion

Question 11

Anode:
This losing of electrons can be shown as: ,,,,,,,.
The Fe++ is called ,,,,,,

Answer 11

-Fe → Fe++ + 2e
a positive iron ion

Question 12

Anode:
An ,,,,, can be positive or negative and is a
,,,,,,,, an atom or a group of atoms

Answer 12

ion
charged particle

Question 13

Anode:
A passive iron atom Fe has ,,,,proton & ,,,,,electrons

Answer 13

26
26

Question 14

Anode:
An iron ion Fe++, has ,,,,,, protons and ,,,,,, electrons

Answer 14

26
24

Question 15

Cathode:
A cathode is ,,,,,, charged area

Answer 15

negatively

Question 16

Cathode:
A cathode is a negatively charged area where there are ,,,,, electrons than needed in its ,,,,,,,.

Answer 16

more
passive state

Question 17

Cathode:
At the cathode the electrons enter into the ,,,,,, to pass back to the ,,,,,

Answer 17

electrolyte
anode.

Question 18

Electrolyte:
An electrolyte is a substance, which will ,,,,,,,and ,,,,,,,

Answer 18

conduct a current and be broken down by it, (dissociate into ions).

Question 19

,,,,,, is the most abundant electrolyte and
also very efficient

Answer 19

Water

Question 20

,,,,,,,, and ,,,,,, in solution are also very efficient
electrolytes.

Answer 20

Acids, alkalis and salts

Question 21

As the electrons pass into the electrolyte it is ,,,,,,, into positive and negative ions, as shown by the formula:,,,,,,,,,,, Simultaneously the electrons couple back with the ,,,,,,, ions to form ,,,,,,,, atoms, which join together ,,,,,, to form hydrogen
gas. This is called being ,,,,,, or ,,,,,,,

Answer 21

dissociated
-2H2O→2H+ + 2OĦ
hydrogen
two full hydrogen
diatomically
evolved
given off from the cathode

Question 22

Electrolyte:
The hydroxyl ions return to the ,,,,, through the electrolyte carrying the ,,,,,,,

Answer 22

anode
electrons.

Question 23

The chemical reaction:
In corrosion, chemical reaction, the formation of corrosion products, only occurs at the ,,,,,,

Answer 23

anode

Question 24

If a structure can be made to be the ,,,,, in a circuit, it will not corrode

Answer 24

cathode

Question 25

The chemical reaction:
The corrosion triangle shows the three elements needed for corrosion to occur are ,,,,,,

Answer 25

anode, cathode and electrolyte.

Question 26

The chemical reaction:
The one most commonly eliminated element is
the ,,,,

Answer 26

electrolyte

Question 27

The chemical reaction:
If ,,,,,, is not in direct contact with anode and cathode, there can be no circuit and so no corrosion.

Answer 27

electrolyte

Question 28

The chemical reaction:
factors can increase the reaction rate, listed below are some of these are; ,,,,,

Answer 28

Temperature
Hygroscopic salts
Aerobic conditions
SRBs or MEM
Bi-metallic contact

Question 29

The chemical reaction:
,,,,,,,and ,,,,,, are the two most common salts,

Answer 29

Sulphates
Chlorides

Question 30

The chemical reaction:
chlorides predominant in ,,,,, environments

Answer 30

marine

Question 31

The chemical reaction:
sulphates predominant in ,,,, and ,,,,.area

Answer 31

industrial
sometimes agricultural

Question 32

The chemical reaction:
By introducing oxygen into the cathodic reaction the number of ,,,,, doubles

Answer 32

hydroxyl ions

Question 33

The chemical reaction:
A ,,,,, metal is one, which will not corrode

Answer 33

noble

Question 34

The chemical reaction:
The degree of activity can be expressed as ,,,,,

Answer 34

potential, in volts

Question 35

The chemical reaction:
The list can be called a ,,,,, list

Answer 35

galvanic

Question 36

The chemical reaction:
when the free potentials of the metals are ,,,,, it can also be called the ,,,,, or ,,,,,,,

Answer 36

known
electromotive forces series or
electrochemical series

Question 37

The chemical reaction:
Mill scale is formed during the ,,,, operation of steel sections eg RSC, RSA, RSJ

Answer 37

rolling

Question 38

The chemical reaction:
The oxides of iron form very quickly at temperatures in ,,,,

Answer 38

excess of 580oC

Question 39

The chemical reaction:
During rolling operation, The first oxide formed is ,,,, the next is ,,,,,, and last of all ,,,,

Answer 39

iron oxide (FeO), wustite,
Fe3O4, magnetite
Fe2O3, haematite

Question 40

The chemical reaction:
These oxides are compressed during the rolling operation to produce ,,,,,

Answer 40

blue mill scale

Question 41

The chemical reaction:
The thickness of mill scale varies from ,,,,

Answer 41

25-100um.

Question 42

The chemical reaction:
When mill scale has been removed by any surface preparation method, it can ,,,,,,

Answer 42

never recur