Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

Difference in galvanising and sacrificial protection

Galvanizing is applying a coat of ZINC to protect iron/steel from rusting. It can be done using electrolysis.
In sacrificial protection, any metal more reactive than iron are used, we attach pieces of the more reactive blocks near (or on) the iron body/pipe and the oxygen reacts with the more reactive metal instead of iron. The blocks have to be replaced often.

 

[Saad Mughal]

i also wrote water in excess in brackets...cant help, learnt it from beginning

Yup.

 

[usama321]

Can u tell me why 2 moles will react?

See the equation of the reaction

 

[Saad Mughal]

So the

So the substance that has less moles/mass will become limiting reactant?

The substance that has less MASS becomes limiting agent.

 

[sourov97]

So the

So the substance that has less moles/mass will become limiting reactant?

not really...u have to compare mole ratio and then decide...
in that reaction 1 mol Ca needed 2mol water, but there was 5.sth mols of water, so water is excess.

 

[Saad Mughal]

same here i was like WHAT as i did not know what limiting factor meant
well i know what limiting factor is but i did not know here

Well, its easy to figure that out by taking in account the moles and the masses/volume.

 

[farhan141]

The substance that has less MASS becomes limiting agent.

Moles too. Right?

 

[farhan141]

not really...u have to compare mole ratio and then decide...
in that reaction 1 mol Ca needed 2mol water, but there was 5.sth mols of water, so water is excess.

Oh ok got it.

 

[ZaqZainab]

galvanizing is to coat the whole Iron surface with Zinc so that the iron does not come in contact with water and air

In sacrifical protection, a more reactive metal is just attached to the Iron, so that it reacts first with the water and air, and corrodes in place of the Iron

can galvanization be by another metal?
wait this is so confusing so basically the difference is that For Galvanizing only using copper,only on iron and everything else is the same as Sacrificial protection is ?

 

[Saad Mughal]

Moles too. Right?

Well yes, so if 5 moles of water are present and only 2 moles are reacting (calculated from mass) so it is in excess.

 

[sourov97]

can galvanization be by another metal?
wait this is so confusing so basically the difference is that For Galvanizing only using copper,only on iron and everything else is the same as Sacrificial protection is ?

galvanising uses zinc, and the other is same as sacrifical protection (which often refers to Mg)

 

[usama321]

can galvanization be by another metal?
wait this is so confusing so basically the difference is that For Galvanizing only using copper,only on iron and everything else is the same as Sacrificial protection is ?

galvanizing is done by Zinc. The whole thing is coated with Zn

On the other hand in sacrifical protection, just a piece or block of a more reactive metal is attached to the Iron, no coating involved

 

[ZaqZainab]

Galvanizing is applying a coat of ZINC to protect iron/steel from rusting. It can be done using electrolysis.
In sacrificial protection, any metal more reactive than iron are used, we attach pieces of the more reactive blocks near (or on) the iron body/pipe and the oxygen reacts with the more reactive metal instead of iron. The blocks have to be replaced often.

for galvanisation can the zic be PLACED near iron or steel

 

[Saad Mughal]

can galvanization be by another metal?
wait this is so confusing so basically the difference is that For Galvanizing only using copper,only on iron and everything else is the same as Sacrificial protection is ?

No it is specifically by Zinc. It is a coating of one or more layers of zinc.
Only using Zinc, and it is coated or applied to the body whereas in Sacrificial Protection you just attach the piece of reactive metal so that oxygen reacts with it instead.

 

[Saad Mughal]

for galvanisation can the zic be PLACED near iron or steel

No a layer of zinc coating is applied.

 

[usama321]

for galvanisation can the zic be PLACED near iron or steel

that would be called sacrifical protection

 

[ZaqZainab]

galvanizing is done by Zinc. The whole thing is coated with Zn

On the other hand in sacrifical protection, just a piece or block of a more reactive metal is attached to the Iron, no coating involved

so if i COAT magnesium with calcium what will this be?

 

[farhan141]

Sodium can be used for Sacr. protection?

Btw Thanks Saad for clearing it out.

 

[usama321]

so if i COAT magnesium with calcium what will this be?

stupidity

 

[Saad Mughal]

so if i COAT magnesium with calcium what will this be?

We never go in that detail, we only study iron protection since rust is hydrated iron (III) oxide and since iron is used in a great percentage, we need to protect it from rusting.