Corrosion inhibitors theories

[ChihebG]

As we know, there are two main corrosion inhibitors theories: Corrosion inhibitor availability and corrosion inhibitor efficiency.
Corrosion inhibitor efficiency: E%=100*(CRu-CRi)/CRu.
Corrosion inhibitor availability: CR=CRi*A+CRu*(1-A).

CRi: Inhibited corrosion rate
CRu: Uninhibited corrosion rate
E%: Corrosion inhibitor efficiency
A: availability fraction of the corrosion inhibitor

How can we calculate the uninhibited corrosion rate (CRu) knowing that CRi is calculated from corrosion prediction model?
And how can we assess the availability fraction of the corrosion inhibitor (A) ?

 

[CoCoE]

CRu may be calculated from any corrosion prediction models, CRi is the actual corrosion rate after inhibition, and I doubt 'A', whether it is available fraction in the service after idozing or the dozing rate?