Correlation between the physical structure of epoxy coatings and their electrochemical impedance response.

EIS is used in commercial high-solidity epoxy-based coatings for steel corrosion protection. Weight determination proves the absorption of water and the release of plasticizers.
this work, commercial high-solid epoxy-based coatings for corrosion protection of steel are sampled and tested by electrochemical impedance spectrum (EIS

. The aim is to analyze the effect of absorbent rate on the physical structure of coating by impedance data analysis. First, the absorption rate is measured by weight analysis on a free-stand-alone film, which is a function of the exposure time of the 0.5 M NaCl solution.
acceptable protocol
weight measurement indicates a loss of mass and is related to the release of plasticizers from the preparation. The compound is metered into the NaCl solution. The water volume fraction is also determined from the high frequency portion of the impedance graph using the linear rules of the mixture. The moisture value obtained from both methods is within an acceptable range. The glass transition temperature (T g) of the dry coating and the coating after different immersion times in the NaCl solution is determined by differential scanning amount heat.
in the form of dielex constants allows for average relaxation time from impedance data analysis. The actual part of the conductivity is also considered. The relationship between these parameter values and the exposure time of the NaCl solution is related to the change of T g. They considered plasticization (absorption) at the beginning of immersion and antiplastication (plasticizer release) that extends exposure time.
for the system under study, parameters representing molecular migration rate can be extracted from impedance spectrum analysis and linked to the modification of the coating's physical structure.
the study was published in September 2020 in issue 146 of Organic Coatings Progress.
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