DM - Rusting

Question 1

why type of process is rusting?

Answer 1

electrochemical process =
electrochemical cells are in the surface of metals; one area is reduced and the other oxidised
created + and - E values

Question 2

what actually is rusting?

Answer 2

iron forming iron oxide
the corrosion of iron

Question 3

what happens during the rusting process?

Answer 3

steel reacts with oxygen and water in the atmosphere causing hydrated iron(III) oxide to form
as its permeable the layers underneath will continue to erode

Question 4

what happens when water comes into contact with the iron?

Answer 4

conc of dissolved O2 is greatest at the edge so oxygen is reduced to hydroxide ions
2e- + 1/2O2 + H2O —> 2-OH

electrons come from the oxidation of iron at centre of the droplet where O2 conc low
Fe —> Fe2+ + 2e-

electrons flow to the edges and the iron ion pass into the solution
Fe2+ + 2-OH —> Fe(OH)2
Fe(OH)2 + O2 —> Fe2O3 * XH2O(s)
|————————–|
RUST

Question 5

what is a sacrificial metal?

Answer 5

any metal with a more negative value then iron
causes eqm to lie to the left so fewer iron ions are formed

Question 6

how can you protect against rusting?

Answer 6

provide barrener e.g paint, oil, grease between metal and atmosphere
organic polymers can be used to make a plastic film