corrosion

Question 1

definition of corrosion

Answer 1

destructive chemical reaction between metal and its environment

Question 2

the main full reaction of corrosion of iron and its two oxidation reactions

Answer 2

2Fe O2 2H2O—>2Fe(oh)2

anodic
Fe—> Fe2+ 4e-
cathodic
02 2h20 4e- —–>4 OH-

Question 3

what is created in - regions of immunity

• regions of corrosion
• passivity

Answer 3

regions of immunity- no corrosion
corrosion- Fe2+
passivity Fe2O3 formed

Question 4

7 types of corrosion

Answer 4

uniform
pitting
crevice
intergranular
galvanic
dealloying
environmental

Question 5

requirements of corrosion?

Answer 5

electrical circuit
moisture (for cathodic reaction )
oxidising agent (for cathodic reaction)
avaliable metal (anode)

Question 6

process of formation of passive layer?

Answer 6

Iron reacts to form Iron ions, which react with hydroxide ions to form Fe(OH)2 which then react with oxygen to form Fe2O3.

Question 7

what is the average passive rate and active rates of corrosion

Answer 7

passive 1.116 um/year active 1.116-116 um/year i think

Question 8

main carbonation of concrete reaction?

Answer 8

2Ca(OH)2 CO2—–>CaCO3+H2O

Question 9

is the carbonation level in the concrete gradual or abrupt?

Answer 9

abrupt ge, like bang bang abrupt. from PH13 to PH 9 just like that

Question 10

How many times is the iron oxides volume than the irons and what does this cause

Answer 10

7x causes expansion of reinforcement , cracking, spalling, delamination.

Question 11

some basic corrosion prevention methods?

Answer 11

membranes, high performance concrete, coating on steel, non corrsive metals, chemical corrsoion inhibitors, (fly ash good for resistivity)

Question 12

Main factors affecting corrosion rate?

Answer 12

oxygen availability
resistivity of concrete
chloride concentration