17/08/13 Week 6 Saturday 2013 Home

Background Research - pH dependence of corrosion
Normal galvanic corrosion occurs more rapidly in acidic solutions than in alkaline ones(taken from Chemistry in Use Book 2 p375).

Link
Standard electrode potential: http://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)

Example:

In galvanic corrosion the half reaction of O_2(g) + 2H₂O_(l) + 4e­^-  → 4OH^-_(aq) has a standard electrode potential of 0.40V where the value is [OH^-] = 1.00mol/L. If this half reaction occurs in a neutral solution of pH of 7 ([OH^-] = 1.0 x 10^-7 mol/L) the non standard electrode potential changes to 0.81V and at pH = 4.00 a further 0.99V. This information suggests that electrode potential increases as acidity increases. If  this is the situation then this half reaction has a greater tendency to occur if the pH decreases (becomes more acidic).