Electronics; Cathodic Protection

Question 1

What is corrosion?

Answer 1

An electro-chemical process that involves minute current flows

Question 2

What do you call the process of producing free electrons which pass within a metal to another site on the metal surface, where it is consumed by the cathodic reaction?

Answer 2

Anodic reaction

Question 3

What are the four parts of a corrosion process?

Answer 3

Anode
Cathode
Electrolyte
Metallic path

Question 4

Where does corrosion occur?

Answer 4

Anode

Question 5

Where does protection occur?

Answer 5

Cathode

Question 6

Where do ions flow (re: corrosion process)

Answer 6

Electrolyte

Question 7

What completes the path between anode and cathode for electrons to flow? (Re: corrosion process)

Answer 7

Metallic path

Question 8

Describe the current flow with regards to the anode

Answer 8

Current flows by chemical means
FROM the surface of the metal
TO the electrolyte.

Question 9

Describe the current flow with regards to the cathode

Answer 9

Current flows by chemical means
FROM the electrolyte
TO the metal

Question 10

At the anode the chemical reaction is a _________ reation

Answer 10

Oxidation (metal LOSING an electron and combining with another element; oxygen)

Question 11

At the cathode the chemical reaction is a __________ reaction

Answer 11

Reduction (cathode GAINING electrons)

Question 12

What kind of material is an electrolyte?

Answer 12

Any material in contact with both anode and cathode that will allow oxidation and reduction reactions to occur

Question 13

What part of a corrosion process includes the source of elements or atoms that are required for ion transfer to and from the metal electrodes

Answer 13

Electrolyte

Question 14

What is the purpose of catholic protection?

Answer 14

To create a corrosion cell in which the structure to be protected is the cathode and therefore protected from corrosion

Question 15

What are the two most common types of cathoduc protection?

Answer 15

Sacrificial anode

Impressed current systems

Question 16

What are the most common materials used for sacrificial anode systems?

Answer 16

Aluminum
Zinc
Magnesium

Question 17

What kind of catholic protection do catholic protection rectifiers provide?

Answer 17

Impressed current cathodic protection

Question 18

What kind of power to cathodic protection rectifiers use? What kind of power do they provide?

Answer 18

Use ac power. Provide dc (is a rectifier!)

Question 19

What are the components of a cathodic protection rectifier?

Answer 19

Adjustable step down transformer
Rectifier stacks
Shunt to measure output current
Meters to indicate output voltage and current
Circuit breakers
Lighting arresters 
Transformer tap connections

Question 20

What are the two types of recifier stacks available?

Answer 20

Selenium plates

Silicon diodes

Question 21

What type of rectifier stack should be used in high voltage or high current applications?

Answer 21

Silicon diode type

Question 22

Which type of rectifier stack is less efficient (has a higher voltage drop)

Answer 22

Selenium type

Question 23

Which type of rectifier stack is less affected by voltage surges?

Answer 23

Selenium type

Question 24

Which type of rectifier stack must be protected from voltage of current spikes by metal oxide varistors?

Answer 24

Silicon diode type

Question 25

Which type of rectifier stack ages over time?

Answer 25

Selenium type

Question 26

On a (manual/automatic) recifier unit, the transformer tap connections normally encircle the “center tap” connections

Answer 26

Manual

Question 27

Which connections on the transformer of a manually controlled rectifier unit provide input to the stacks? Which are the output from the stacks?

Answer 27

Center tap connections are the input to the stacks

Negative and positive lugs are the output from the stacks