A Design of Experiment (DOE)approach was used to investigate the effect of hydrogen sulfide (H2S),carbon dioxide (CO2) and brine composition on the corrosion rate of carbon steel. Three of the most common experimental design approaches (Full Factorial, Taguchi L4,and Alternate Fractional) were used to evaluate the results. this work concluded that: 1) CO2 and brine both have significant main and two-factor effects on corrosion rate, 2) H2S concentration has a moderate effect on corrosion rate, and 3) higher total dissolved solids (TDS) brine compositions appear to force gases out of solution, thereby decreasing the corrosion rate of carbon steel. The Full Factorial Design correctly identified no independent vnriables and the significant interactions between CO2H2S and CO2. Brine on corrosion rate. The two fractional factorial experimental methods resulted in incorrect conclusions. The
Taguchi L4 method gave misleading results as it did not identify H2S as having a positive effect on corrosion rate, and only identified the strong interactions in the experimental matrix. The Alternate Fractional design also yielded incorrect interpretations with regard to the effect of brine on corrosion. Tlis study has shown that reduced experimental designs (e.g., half fictional) maybe inappropriate for distinguishing the synergistic interactions Iikely tn form in chemically reactive systems. Therefore, based upon the size of the data set collected in this work, we recommend that full factorial designs be used for corrosion evaluations. When the number of experimental variables make it impractical to perform a full factorial design, the aliasing relationships should be caretidly evaluated.
Key Words: design of experiments, Taguchi, corrosion evaluations, CO2, H2S, brine