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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: magnus on February 05, 2019, 03:55:45 AM

Title: sacrificial anode
Post by: magnus on February 05, 2019, 03:55:45 AM

Which of the following metals can behave as a sacrificial anode in an iron corrosion protection system (E ° (Fe2 + / Fe) = - 0.44 V).
(Ni2+/Ni)=-0.25 V
(Cu2+/Cu)=+0.34 V
(Pb2+/Pb)=-0.126 V
(Mn2+/Mn)=-1.18 V

I was thinking of Cu, but I'm not sure in semi-reaction

Title: Re: sacrificial anode
Post by: chenbeier on February 05, 2019, 05:43:19 AM

It can be only a metal with a redox potential less as -0,44 V. The metal normally is innoble like Magnesium, Zinc or Aluminium.

Title: Re: sacrificial anode
Post by: Enthalpy on February 05, 2019, 11:36:10 AM

I haven't seen aluminium in this role, despite it's cheaper than magnesium. Redox potential isn't the whole picture.

If someone has made experiments about galvanic corrosion, I'd gladly read the first-hand results. My single attempt told that corrosion couples change nothing, at least with the metal purity common in mechanical engineering.