Water uptake in protective organic coatings and its reflection in measured coating impedance

Miszczyk, A.; Darowicki, Kazimierz

doi:10.1016/j.porgcoat.2018.03.002

Cited by 53 publications

(22 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, this approximation is only valid for randomly distributed spherical water inclusions; finite element analysis showed that cylindrical inclusions can produce a much greater change in capacitive response relative to spherical ones because the formation of percolation paths is more possible [ 97 ]. Therefore, a simple application of Equation (5) may overestimate the true water content regardless of inclusion geometries [ 98 , 99 ]. It should also be noted that Equation (5) assumes constant geometrical parameters for an epoxy coating over time and thereby ignores swelling effects.…”

Section: Mass Transport Through Coating Materialsmentioning

confidence: 99%

A Critical Review of the Time-Dependent Performance of Polymeric Pipeline Coatings: Focus on Hydration of Epoxy-Based Coatings

Zargarnezhad

Asselin

Wong³

et al. 2021

Polymers

View full text Add to dashboard Cite

The barrier performance of organic coatings is a direct function of mass transport and long-term stability of the polymeric structure. A predictive assessment of the protective coating cannot be conducted a priori of degradation effects on transport. Epoxy-based powder coatings are an attractive class of coatings for pipelines and other structures because application processing times are low and residual stresses between polymer layers are reduced. However, water ingress into the polymeric network of these coatings is of particular interest due to associated competitive sorption and plasticization effects. This review examines common analytical techniques for identifying parameters involved in transport in wet environments and underscores the gaps in the literature for the evaluation of the long-term performance of such coating systems. Studies have shown that the extent of polymer hydration has a major impact on gas and ion permeability/selectivity. Thus, transport analyses based only on micropore filling (i.e., adsorption) by water molecules are inadequate. Combinatorial entropy of the glassy epoxy and water vapor mixture not only affects the mechanism of membrane plasticization, but also changes the sorption kinetics of gas permeation and causes a partial gas immobility in the system. However, diffusivity, defined as the product of a kinetic mobility parameter and a concentration-dependent thermodynamic parameter, can eventually become favorable for gas transport at elevated temperatures, meaning that increasing gas pressure can decrease selectivity of the membrane for gas permeation. On the other hand, reverse osmosis membranes have shown that salt permeation is sensitive to, among other variables, water content in the polymer and a fundamental attribute in ionic diffusion is the effective size of hydrated ions. In addition, external electron sources—e.g., cathodic protection potentials for pipeline structures—can alter the kinetics of this transport as the tendency of ions to dissociate increases due to electrostatic forces. Focusing primarily on epoxy-based powder coatings, this review demonstrates that service parameters such as humidity, temperature, and concentration of aggressive species can dynamically develop different transport mechanisms, each at the expense of others. Although multilayered coating systems decrease moisture ingress and the consequences of environmental exposure, this survey shows that demands for extreme operating conditions can pose new challenges for coating materials and sparse data on transport properties would limit analysis of the remaining life of the system. This knowledge gap impedes the prediction of the likelihood of coating and, consequently, infrastructure failures.

show abstract

Section: Mass Transport Through Coating Materialsmentioning

confidence: 99%

A Critical Review of the Time-Dependent Performance of Polymeric Pipeline Coatings: Focus on Hydration of Epoxy-Based Coatings

Zargarnezhad

Asselin

Wong³

et al. 2021

Polymers

View full text Add to dashboard Cite

show abstract

“…Miszczyk et al further developed methods to correlate impedance data from electrochemical impedance spectroscopy to obtain the corresponding capacitance values that were found to vary with gravimetric data of amine-cured epoxy coatings immersed in water. 35…”

Section: Introductionmentioning

confidence: 99%

Unraveling the Mechanistic Origins of Epoxy Degradation in Acids

Lim

Gan

2019

ACS Omega

View full text Add to dashboard Cite

Water diffusion into polymers like thermosetting epoxies is well-studied; however, comparably little has been reported thus far on the related but very different mechanism of acid diffusion and the corresponding influence on material degradation. The diffusion of hydrochloric acid into an amine-cured epoxy system was studied in this work using gravimetric analysis and dielectric monitoring concurrently, and the mass uptake behavior was observed to differ significantly compared with water diffusion, faster by an order of magnitude. A unique 3-stage diffusion of acid into epoxy was observed due to the influence of Coulombic interactions between oppositely charged ionic species diffusing at different rates. Material characterization studies have revealed that the dominant degradation mechanism is physical in nature, with the formation of surface cracks driven by the swelling stresses due to the core–shell swelling behavior in highly concentrated hydrochloric acid, leading to an erosion-type degradation phenomenon. The insights gained from understanding acid electrolyte diffusion could serve to design a more effective and efficient process to enable thermoset recycling by facilitating rapid material breakdown or the design of acid-resistant materials for various applications in chemical storage tanks, batteries, and protective coatings in a corrosive environment.

show abstract

“…Moisture absorbed by the coating could also accelerate the nanofibre shell material (PVA) dissolution. [ 47–59 ] Thus, GACE from the cut‐off nanofibres showed an accelerated dissolution in the NaCl solution. Iron ions reacted with GACE immediately and formed a chelation film.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterisation of an iron‐ion‐responsive coating with core–shell electrospun fibres containing a chelation agent

Song

Shi

Han³

et al. 2021

Materials & Corrosion

View full text Add to dashboard Cite

A self‐healing coating containing an electrospun nanofibre encapsulating 3,4,5‐trihydroxy benzoic acid cyclohexyl ester (GACE) was prepared. Scanning electron microscopy and transmission electron microscopy demonstrated that the nanofibre had a core–shell structure. The shell thickness of the electrospun fibre was approximately 270 nm, while the core thickness was approximately 380 nm. The self‐healing process of the coating containing GACE nanofibres over a carbon steel surface was simulated in a 3.5 wt% NaCl solution for 30 days. Fourier‐transform infrared spectroscopy analysis revealed that the synthesised GACE reacted with iron ions and formed a stable Fe–O–C compound, which could repair the scratched coating. The self‐repair performance was evaluated through electrochemical measurements, and then a healing model was developed.

show abstract

Water uptake in protective organic coatings and its reflection in measured coating impedance

Cited by 53 publications

References 31 publications

A Critical Review of the Time-Dependent Performance of Polymeric Pipeline Coatings: Focus on Hydration of Epoxy-Based Coatings

A Critical Review of the Time-Dependent Performance of Polymeric Pipeline Coatings: Focus on Hydration of Epoxy-Based Coatings

Unraveling the Mechanistic Origins of Epoxy Degradation in Acids

Synthesis and characterisation of an iron‐ion‐responsive coating with core–shell electrospun fibres containing a chelation agent

Contact Info

Product

Resources

About