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Ecorr of FeSn2

I need to know the corrosion potential or equilibrium potential of FeSn2. As has been mentioned it is more cathodic than steel.

Thank you,

Luhulima Desiree
student (researcher) - Helsinki, Uusimaa, FINLAND
2004

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2004

I am not sure you can get an equilibrium potential for a material such as FeSn2 because it is an intermetallic compound that does not have an electrochemical equilibrium. The equilibrium potential is when the forward reaction current equals the reverse reaction current (i.e., I(f) = I(r) = I(o). If you try to electrodeposit FeSn2, all you will get is a mixture of Fe and Sn being co-deposited, you would then need to heat treat it to form the alloy FeSn2. On the other hand, the corrosion potential that is taken up by a metal in a given electrolyte will depend on the magnitude of the exchange currents for the various possible equilibria, the number of possible electrode reactions that can occur, film formation, complex ion formation, impurities in the solution, temperature etc. In the majority of corrosion reactions, more than 1 electrode process is occurring so the actual potential is the resultant of 2 or more electrode processes. This is known as the corrosion potential, or the mixed, compromise or reaction potential. This is very well exhibited by the electrochemical dissolution of FeSn2 in NaOH, which occurs at about 70C or more. At higher current densities the reaction potential is about -350 to -400mV (vs Hg/HgO), but at lower current densities there is a two stage reaction, where the first stage is at about -840mV (vs Hg/HgO) followed by the higher potential reaction. This is because the alloy is disrupted and the kinetics follow the formation of Fe(OH)2 that is oxidised to Fe(OH)3 as well as the dissolution of Sn to Sn(OH)2. In this system, oxygen evolution starts at +630mV (vs Hg/HgO). There will be a similar process if the reaction is done in acid (say HCl), but the potentials will be different.

I suggest you get some FeSn2 from some tinplate and measure the corrosion potentials in different electrolytes. It is easy to do and shouldn't take long. It is also good practical experience!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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Thank you. The solution I interested in is NaCl 0.3 % or artificial seawater at room temperature. I have tried to get FeSn2 (as well from ti plate) with no good result.

Luhulima Desiree
- Helsinki, Uusimaa, FINLAND
2004