Expert options allow user to explore how user-defined electrochemical reactions alter the corrosion process. Two different dialogs are open depending on which corrosion process is dominant, electrochemical or chemical reactions.

Expert Options for Electrochemical Reactions

A number of anodic reactions and cathodic reactions can be added into the corrosion process as additional electrochemical reactions. Before adding a user-defined reactions, users have to create a text file for each additional reaction in which all parameters needed in the calculation are provided in a certain format.

Definition of Reaction Files

For example, you want to explore how a certain type of stainless steels can be corroded in the corrosive environment. First step is to locate a folder called Data which most likely resides within the same place as your downloaded FREECORP.xla file. Open Data folder, and create a new text file with the name that you intend to use for the name of this reaction. In this case, the name of this text file would be ‘StanlessSteel_dissolution.REA’. Note to change the extension of the text file to ‘REA’. Now you can input all necessary parameters for electrochemical calculation.

The format of user-defined reaction curve files (*.REA) is restricted to following, otherwise it won’t be recognized. The file name is ‘StainlessSteel_dissolution.REA’.

    Name,StainlessSteel_dissolution
    Type,Anodic
    Temperature,293.15
    Reversable Potential (Erev),-7.00E-01
    Exchange Current Density (io),1.50E-05
    Tafel Slope (b),0.08
    Limiting Current Density (ilim),0
    Passivation Potential (Epas),-0.4
    Passivation Current Density (ipas),5.00E-03
    Pitting Potential (Epit),-0.15

Reaction files can be created using text editor (like Notepad) or using MS Excel (see figures below). If user decided to use Notepad, care should be taken to save file with REA extension. If user decides to use MS Excel, the file should be saved as CSV text file, and then later renamed to have .REA extension.



There are 10 parameters to be given by users in this file. Note that the portion before each comma, which is the parameter name, is fixed and cannot be changed. Users are only expected to give the data after comma.

Using Reaction Files in Expert Dialog

After corrosion calculation, user can choose new reaction curves to participate in corrosion calculation by clicking Expert button assuming that the desired reaction curve file has been created as described above. An Add or Remove Electrochemical Model Reactions dialog is populated. Selected Reactions list shows all the reactions that are currently participating in the corrosion calculation. Available Anodic Reactions list shows all the available anodic reactions expect those that are already in Selected Reactions list. Available Cathodic Reactions list shows all the available cathodic reactions expect those that are already in Selected Reactions list.



User can move reactions from/to model to configure reactions that he/she wants to explore. User can choose any available cathodic/anodic reactions by clicking >> button. Also, user can remove any selected reactions by clicking << button. However, in order to make sure user-defined reaction is compatible to current corrosion model, temperature is checked before adding this reaction to Selected Reactions list. Additionally, at least one anodic reaction and one cathodic reaction is required in Selected Reactions list. User can either disregard model reconfiguration by clicking Cancel button, or proceed with model reconfiguration by clicking OK button.

If user selects to reconfigure corrosion model, the program reads all the data needed in calculation from reaction curve files (*.REA), adds them to model calculation, recalculates new corrosion rate, and display updated diagram for user examination.

There are 6 default reaction files in the folder corresponding to 6 default reactions - ‘Iron_dissolution’, ‘H+_reduction’, ‘H2O_reduction’, ‘H2CO3_reduction’, ‘HAc_reduction’, ‘O2_reduction’. User can add his/her own files with required parameters as shown earlier. If the format of user-defined reaction curve file is correct, it will be shown in Available Anodic Reactions/Available Cathodic Reactions list.


Expert Options for H₂S Corrosion

After corrosion calculation, user can choose his/her preferred species by clicking Expert button. An Add or Remove H₂S Corrosion Model Species dialog is populated (see figure). Selected Species list shows all the current selected species which participate in the corrosion calculation. Available Species list shows all the available species expect for ones that are already in Selected Species list. There are only 4 species – ‘H₂S’, ‘H⁺’, ‘HAc’ and ‘CO₂’. User can choose any available species by clicking >> button. Also, user can remove any selected species by clicking << button. But species ‘H₂S’ cannot be removed from Selected Species list, because it is necessary for the H₂S corrosion.