SYNERGISTIC EFFECT OF SEAWATER ENVIRONMENTAL FACTORS ON CARBON STEEL CORROSION RATE

摘要

Seawater is an aggressive, very corrosive, complex composition of different minerals covering about 70% of the earth's surface that affects nearly all structural materials to some extent. Since seawater is a complex solution of many salts with various levels of physical and chemical parameters, the individual effect of each factor affecting the corrosion behavior is not readily separated, as is the case for a simple salt solution and an alteration in one may affect the relative effect magnitude of others, which illustrates the importance of synergistic analysis of dominant parameters. The synergistic effect of environmental factors on corrosion rate of carbon steel (AISI 1045) has been assessed in aerated synthetic seawater, using potentiodynamic polarization scan. The major environmental parameters considered are salinity, velocity, pH and temperature. A quantitative full two-level factorial experimental design method was applied to study the individual contribution percentage of each parameter on changing the average value of corrosion rate, as well as their interactive contributions. Because of the significant weakness of quantitative analysis in description and justification of variation direction the qualitative analysis has been assessed. The results show that the most contribution factor obtained by quantitative analysis is not always the most effective one obtained by qualitative analysis.