need help with corrosion !! >< (1 Viewer)

[denisec]

hi

i cant seem to find much information on why stainless steel and brass is so resistant to corrosion while high tensile steel isnt.??

wat is the composition of high tensile steel..?

anyone noe.? =S

 

[tennille]

Stainless steel consists of carbon, chromium and nickel. It does not corrode as it forms a protective chromium oxide layer.

I found this website based on the corrosion resistance of various metals:

http://www.corrosionsource.com/events/intercorr/techsess/asm/asm2.htm

Hopefully that will help you with brass, which contains copper and zinc.

 

[denisec]

i found this article but im kinda confused about wat its saying..

how come it seems to say that the rate of corrosion increases as temperature increases yet..it mentions sumthing about wen the temperature increases the solubility of water decreases etc..lowering the rate of reaction..

http://www.ias.ac.in/matersci/bmsoct2002/375.pdf

 

[rama_v]

i found this article but im kinda confused about wat its saying..

how come it seems to say that the rate of corrosion increases as temperature increases yet..it mentions sumthing about wen the temperature increases the solubility of water decreases etc..lowering the rate of reaction..

http://www.ias.ac.in/matersci/bmsoct2002/375.pdf

Basically as temperatures increase the level of oxygen able to dissolve in the water decreases, hence while higher temperatures increase the rate of reaction (due to reaction kinetics), due to lower oxygen levels, corrosion is decreased. Think of it like in the Haber Process, where you need a balance of temeperature thats not too hot (because its an exothermic reaction; asper le chatlier's the reaction would be pushed towards the reactants side) but not too cold either (or else the reaction would take forever to go to completion).

 

[denisec]

then if the temp is increased n causes a decrease in oxygen levels, hence decreased corrosion..then is it wrong to say that increased temperature increases rate of corrosion..? coz that kinda contradicts is doesnt it.?

 

[rama_v]

then if the temp is increased n causes a decrease in oxygen levels, hence decreased corrosion..then is it wrong to say that increased temperature increases rate of corrosion..? coz that kinda contradicts is doesnt it.?

Increased temperatures increase the rate of any reaction. However reduced oxygen levels reduce corrosion, because oxygen is required for corrosion to occur.It's not a contradiction because the temperature affects the reaction in two distinct ways. I wouldn't be surprised however if the overriding factor is the temperature and its affect on the rate of reaction - the level of DO (which is somewhat dependant on temperature) doesn't come into play that much (at least it didn't in the experiments we performed at school last year).

 

[denisec]

thanx...

btw..could anyone confirm the statement that the process of corrosion is endothermic ??