The metal oxidation takes place by an
anodic reaction and reduction takes place through a cathodic reaction:
From the anodic branches, it is possible to observe a change in its slope to potentials slightly above the corrosion potential; this suggests that the presence of [Nd.sup.3+] ions also affects the
anodic reaction of the electrochemical corrosion process of the API X70 steel.
The
anodic reaction releases electrons, while the cathodic reaction consumes electrons.
Reaction (11) factually unites two electrochemical systems: cathodic reaction (2) and
anodic reaction (8).
Considering the signal of current in the mapping, the negative current value is correlated with cathodic reaction, mainly occurring on steel surface, while the positive current values are correlated with
anodic reaction, that occur at the zinc primer surface.
It is seen that the plating over potential instantly goes back to positive and thus the
anodic reaction of equation 1 will dominates and the plated lithium converts to lithium ions and re-insert in graphite through two steps of electrochemical reactions.
And, the primary
anodic reaction is the dissolution of iron:
These results indicate that GAI gum acts as a mixed-type corrosion inhibitor, predominantly controlled by
anodic reaction [31].
The slope of 0.0203 [+ or -] 0.0008 volts/pH between 4 and 10 does not correspond to any known single solution oxidation process and it is likely that the
anodic reaction is a mixture of anodic oxidation of hydrogen that was adsorbed onto the platinum electrode at -1.0 volts vs.
In this study, the cathodic reduction of oxygen was thought to be dominant and the effect of the
anodic reaction at the scratch was presumably small.
Hence, for study of the corrosion mechanism of pure aluminum in alkaline solution, it is enough to consider indirect metal dissolution by consecutive film formation and dissolution as a partial
anodic reaction.