CATHODIC PROTECTION

4 things that must be present for corrosion to occur

• anode,cathode, metallic pathway, electrolyte.

• all

• ?

electrons flow from anode to cathode through metallic pathway. the ions flow from anode to cathode through the electrolyte and that wastage of metal, corrosion, occurs at the

• anode

• metallic pathway

• cathode

• electrolyte

cathodic protection 1 amp for 1 yr removes 23.5lbs of

• iron

• coating

• solvents

• none

cathodic protection is used to protect structures, which are ? we will call the environment from which the structure is being protected the electrolyte.(so water is electrolyte)

• buried

• submerged in water

• used contain liquids, (primarily water based or contain some water)

• all

cathodic makes use of a flow of electric current through whatever the structure is

• buried in

• submerged in

• or what ever structure contains.

• all

one reason for applying coatings to structure, to provide electrical insulation between the structure and electrolyte.

• true

• false

cathodic protection definition

• is the reduction or elimnation of the corrosion by making the structure to be protected a cathode by means of an impressed current or attached to a galvanic anode(magnesium, aluminum, or zinc)

• none

how cathodic protection works

• cathode is the electrode, prior to applying cathodic protection,(steel has cathodic and anode areas) if the anodic areas of steel are converted to cathode, then entire steel would be a cathode, corrosion will be satisfactorily controlled.

• yes

how cathodic protection works according to nace 2 book

• direct current electricity to a corroding metal, cause structure to become cathodic.

• D.C Power + to anode, - to pipe(cathode), direct current is flowing from the anodic areas into the soil, through the soil and onto the cathodic areas, and back through the pipe itself to complete the circuit.

• driving voltage(galvanic potential between anode & cathode) amount of current is limited by resistivity of the enviroment(ohm-centimeters)& degree of polarization at anodic & cathodic areas.

• corrosion results at the current discharge from metal to electrolyte(soil) at anodic areas. will current flows from enviroment to pipe(cathodic areas) no corrosion

• all

cathodic protection current flows into the environment from a special ground connection called

• ground bed

• soil connection gel

• sol connection

• grounded soil