Abstract
In previous work, the importance of taking the time-domain into account when studying corrosion inhibitor-containing electrochemical systems was highlighted. In this work, odd random phase electrochemical impedance spectroscopy (ORP-EIS) is applied as the electrochemical tool to study the time-effect by the evaluation of the non-stationarities per frequency decade over time for the screening of different silica- and phosphate- based corrosion inhibitors for hot-dip galvanized steel and possible corrosion inhibitor synergism. This serves as the basis for the interpretation of the results obtained from different macroscopic electrochemical techniques such as potentiodynamic polarization (PP), open circuit potential (OCP) with superimposed linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) measurements. The analysis of the time-domain shows that all systems have a system-specific ‘stabilization’ time which affects the interpretation of the results obtained from the macroscopic electrochemical techniques. Furthermore, these results indicate that all corrosion inhibitors tested exhibit corrosion protective action and that the combination of both silica-based corrosion inhibitors show synergistic action on hot-dip galvanized steel.
Highlights
In quest for eco-friendly corrosion inhibition of metals, the replacement of chromate corrosion inhibitors is of particular interest nowadays [1]
This serves as the basis for the interpretation of the results obtained from different macroscopic electrochemical techniques such as potentiodynamic polarization (PP), open circuit potential (OCP) with superimposed linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) measurements
odd random phase electrochemical impedance spectroscopy (ORP-EIS) is applied as the electrochemical tool to study the timeeffect by the evaluation of the non-stationarities per frequency decade over time
Summary
In quest for eco-friendly corrosion inhibition of metals, the replacement of chromate corrosion inhibitors is of particular interest nowadays [1]. Rare-earth based corrosion inhibitors, vanadium compounds, lithium-based corrosion inhibitors, silica-based corrosion inhibitors and phosphate-based corrosion inhibitors present examples of categories of promising alternatives for a variety of metal substrates [1,2]. It has been stated that the replacement of chromate corrosion inhibitors will require synergistic combinations of protective chemistries, which, to date, need to be identified and characterized mainly experimentally with, for example, high-throughput methods [3]. Silicates are known to form complex colloidal structures in aqueous solutions with characteristic physicochemical properties such as its equilibrium and reactivity [5]. The protective properties depend highly on the pH and the salt concentration in the solution [5]
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