Evaluation of corrosion inhibitors performance using real-time monitoring methods

Abstract

The implementation of real-time corrosionmonitoring techniques can provide a reliable mechanism for detecting the overall effectiveness of chemical treatment programs and contribute to the selection and implementation of an adequate corrosion inhibitor system. Inadequate corrosion monitoring can result in an increase of both uniform and localized (pitting) corrosion activities which can lead to premature material failures. The present research was undertaken to ascertain whether linear polarization resistance (LPR), harmonic analysis (HA), and electrochemical noise (EN) in combination are suitable for the study of performance of corrosion inhibitors under a wide variety of conditions; for example, in the absence and the presence of hydrocarbons with or without the addition of corrosion inhibitors. The findings showed questionable results regarding the usefulness of the pitting factor derived from EN and HA data. In addition, statistical parameters were obtained, such as skew and kurtosis, and these results were compared with the pitting factor.

Corrosion studies of mild steel in sulphuric acid medium by acidimetric method

“…Fe 2+ + HOH = [FeOH] + + H + (9) It must be, however, considered that factors which affect the acidity of a salt solution are mainly size, charge density of the cation and nature of the solution. Ion of small size and high charge easily hydrolyses to yield considerable amount H + in aqueous solution to affect acidity, with Fe 3+ and Al 3+ being good examples [11,12]. Iron(II) ion is not too small and the charge is not too high either, so the extend of hydration will not be significant to alter the H + level to make the results unreliable.…”

“…A prepared coupon as reported above was weighed and then immersed in 60 mL of the acid solution in a 100 mL beaker applying the above conditions and procedure. Upon retrieval the coupon was washed several times in distilled water, degreased in ethanol and then immersed in acetone then kept in a desiccator to bring it to ambient temperature before determining the final weight and the difference in weight taken [11,16]. The same procedure was repeated upon introduction of various concentrations of the urea into the acid solution.…”

“…where W 1 and W 0 are weight losses in grams in the presence and absence of inhibitors respectively [11].…”

“…In order to ascertain the reliability of the method the results generated were, thus, compared with those of weight loss technique using same inhibitors. The weight loss technique has, indeed, been acclaimed as the best and simplest of all corrosion monitoring techniques [10,11].…”

On the importance of time-resolved electrochemical evaluation in corrosion inhibitor-screening studies

“…Corrosion inhibition mechanisms depend on several parameters that are, one way or another, associated with the properties of basic constituents of the corrosion system, that is, the inhibitor, metal (oxide) surface and electrolyte 5,6 . Some of these parameters may vary during corrosion leading to a change of the inhibitor performance [7][8][9] . The selection becomes more unreliable when several corrosion inhibitors are screened and evaluated at only one specific exposure time.…”