INTERNAL CORROSION

Question 1

Sweet corrosion

Answer 1

CARBON DIOXIDE CO2

Question 2

may exist when fertilizers contact metal surface and may be inhibited using water.

Answer 2

AMMONIA NH3

Question 3

it is often in the form of SCC. It can also be reduced by stress relieving storage tanks before exposure to this corrosive substance.

Answer 3

AMMONIA NH3

Question 4

This is corrosion is controlled by the formation of iron carbonate on the metal surface which can cause pitting if the protective scale is damaged.

Answer 4

CARBON DIOXIDE CO2

Question 5

In the presence of water, it may form carbonic acid (H2CO3) and the corrosion rate is affected by temperature, velocity, pressure, and pH.

Answer 5

CARBON DIOXIDE CO2

Question 6

Damage that occurs at the solid/liquid interface under conditions of turbulent flow as a result of the formation and rapid collapse of cavities or bubbles within a liquid.

Answer 6

CAVITATION CORROSION

Question 7

Remedies include changing vapor pressure and material selection.

Answer 7

CAVITATION CORROSION

Question 8

This is caused by a greenish yellow gas or liquid which is utilized in water purification, bleaches, and mustard gas.

Answer 8

CHLORINE CL2

Question 9

It is commonly used in swimming pools. It can attack iron, steel, aluminum, nickel, stainless steel, copper, and titanium but attack is minimized if corrodent kept dry but titanium it should be wet.

Answer 9

CHLORINE CL2

Question 10

A conjoint action involving corrosion and erosion in the presence of a moving corrosive fluid or a material moving through the fluid leading to an accelerated loss of material.

Answer 10

EROSION CORROSION

Question 11

This type of corrosion does not require the presence of a liquid electrolyte, but usually involves the presence of oxidizing and reducing gases which affect the formation of protective oxide scales.

Answer 11

HIGH TEMPERATURE

Question 12

Some of the effects or issues related to this corrosion are nitriding, carburization, internal oxidation, hydrogen attack, and halide attack.

Answer 12

HIGH TEMPERATURE

Question 13

this produces iron sulfide as a by-product and also damages metal by causing embrittlement to hard alloys and blistering to softer alloys.

Answer 13

HYDROGEN SULFIDE H2S

Question 14

Unaffected by velocity. known as sour corrosion.

Answer 14

HYDROGEN SULFIDE H2S

Question 15

One of the few that attacks glass, therefore the corrodent can only by stored in plastic or teflon containers.

Answer 15

HYDROGEN FLUORIDE HF

Question 16

This is utilized to purify aluminum and uranium

Answer 16

HYDROGEN FLUORIDE HF

Question 17

Similar to wet chlorine corrosion.

Answer 17

HYPCHLORITE

Question 18

It is encountered in bleaching, sanitizing, deodorizing, and waste treatment applications.

Answer 18

HYPOCHLORITE

Question 19

Sodium version called liquid bleach

Calcium version is solid called bleaching powder.

Answer 19

HYPOCHLORITE

Question 20

Lower temperatures will greatly reduce the corrosion rate of this corrodent.

Answer 20

HYPOCHLORITE

Question 21

Caused by a high velocity fluid or gas striking the internal surfaces of a structure, in which the fluid or gas often contain solid particles.

Answer 21

IMPINGEMENT

Question 22

May be the result of impurities retained from the original extractive processes, the inclusions and imperfections introduced in casting and forming, or structure variations caused by heat treatment.

Answer 22

METTALURGICAL

Question 23

This form of corrosion may be encountered when it is made from ammonia.

Answer 23

NITRIC ACID HNO3

Question 24

It is a colorless, corrosive, toxic liquid that is an important industrial raw material that even attacks copper and high carbon 304 stainless steel.

Answer 24

NITRIC ACID HNO3

Question 25

Includes chemicals such as
ascetic acid CH3COOH
propionic acid CH3CH2COOH
formic acid HCOOH

Answer 25

ORGANIC ACID

Question 26

It is considered weak compared to others such as hydrochloric and sulfuric acid

Answer 26

ORGANIC ACID

Question 27

The gas that is considered the most corrosive.

Answer 27

OXYGEN O2

Question 28

It can be removed mechanically or chemically and is normally found in surface equipment

Answer 28

OXYGEN O2

Question 29

The use of plastic materials or internally plastic coating is a fairly common practice when this corrosion is expected. Cement lining is also effective.

Answer 29

OXYGEN O2

Question 30

Although not an actual form of corrosion, it can negatively affect production and transportation of products by restricting flow. It is affected by temperature, pressure and pH.

Answer 30

SCALE FORMATION

Question 31

Most carbonate, sulfate and iron compound scales can be prevented with scaling inhibitors and dissolved with acidic chemical solutions.

Answer 31

SCALE FORMATION

Question 32

Requires tensile stress, specific environmental conditions, and a specific set of mettalurgical factors.

Answer 32

STRESS CORROSION CRACKING SCC

Question 33

Increased levels of zinc in carbon steel alloys reduce this corrosion.
Well bonded coating will prevent this form of corrosion externally.

Answer 33

STRESS CORROSION CRACKING SCC

Question 34

Both low and high pH electrolytes are conducive to this corrosion.

Answer 34

STRESS CORROSION CRACKING SCC

Question 35

Cracking of a metal under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide H2S.

Answer 35

SULFIDE STRESS CORROSION

Question 36

Dependent mainly on the temperature and chemical concentration of the corrodent.

Answer 36

SULFURIC ACID H2SO4

Question 37

It is only slightly corrosive at low temperatures and flow velocities.

Answer 37

SULFURIC ACID H2SO4

Question 38

Above 70% can be used with ordinary carbon steel.

Below 70% chemical lead is commonly utilized.

Answer 38

SULFURIC ACID H2SO4

Question 39

Results from stresses related to welding processes.

Answer 39

WELDMENT

Question 40

Accelerated by stress concentrations, material properties, fabrication, and weld size and quality.

Answer 40

WELDMENT

Question 41

Remedies include the use of proper weld procedures, correct cooling procedures (effective heat treatment), and proper technique.

Answer 41

WELDMENT