Data from: Effect of pH regulation by microbes on corrosion behaviour of duplex stainless steel 2205 in acidic artificial seawater environment

Sulphate reducing bacteria (SRB) can regulate environmental pH because of
their metabolism. Since local acidification results in pitting corrosion,
the potential capacity of pH regulation by SRB would have important
consequences for electrochemical aspects of the bio-corrosion process.
This study focussed on identifying the effect of pH on the corrosion of
duplex stainless steel (DSS) 2205 in a nutrient rich artificial seawater
medium containing SRB species, Desulfovibrio vulgaris. DSS samples were
exposed to the medium for 13 days at 37 0C at pH ranging from 4.0 to 7.4.
The open circuit potential value (OCP), sulphide level, pH and number of
bacteria in the medium were recorded daily. Electrochemical impedance
spectroscopy (EIS) and potential dynamic polarization were used to study
the properties of the films and corrosion behaviour of the material.
Inductively coupled plasma mass spectrometry (ICPMS) was used to measure
the concentration of cations Cr, Fe, Ni, Mo, Mn in the experimental
solution after 13 days. Scanning electron microscopy (SEM) and Energy
Dispersive X-Ray Spectroscopy (EDX) were used for surface analysis. The
results showed the pH changed from acidic values set at the beginning of
the experiment to approximately pH 7.5 after 5 days due to bacterial
metabolism. After 13 days, the highest iron concentration was in the
solution that was initially at pH 4 accompanied by pitting on the
stainless steel. Sulphide was present on all specimens but with more
sulphide corrosion products at pH 4. The results of this study suggest
that the corrosion process for the first few days exposure at low pH was
driven by pH in solution rather than by bacteria. The increasing pH during
the course of the experiment slowed down the corrosion process of
materials originally at low pH. The nature and mechanism of SRB attack on
duplex stainless steel at different acidic environments are discussed.