Mapping Water Uptake in Organic Coatings using AFM-IR
Professor Stuart Lyon of the University of Manchester, a Blue Scientific customer, has published a paper about mapping water uptake in organic coatings using AFM-IR.
Water Uptake in Organic Coatings
Paints are commonly used to isolate metals from corrosive environments. The breakdown of protection offered by organic coatings over long periods of time is an important process in corrosion science. Corrosion initiation mechanisms caused by macroscopic defects have been thoroughly investigated, but the failure of seemingly intact organic coatings on steel is not fully understood. This deterioration is investigated by Professor Stuart Lyon in his paper “Mapping Water Uptake in Organic Coatings using AFM-IR”. Using the Anasys NanoIR2, AFM-IR analysis was used to establish whether water uptake was heterogeneous.
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[hr]Abstract
The proposed mechanism for breakdown of an intact organic coating in contact with electrolyte: formation of hydrophilic pathways and the subsequent generation of an ionic transport channel leading to a localised corrosion spot.
The long-term failure of seemingly intact corrosion resistant organic coatings is thought to occur via the development of ionic transport channels, which spontaneously evolve from hydrophilic regions on immersion, i.e., as a result of localised water uptake. To this end, we investigate water uptake characteristics for industrial epoxy–phenolic can coatings after immersion in deionised water and drying. Moisture sorption and the changing nature of polymer-water interactions are assessed using FTIR for dry and pre-soaked films. More water is found to be absorbed by the pre-soaked coatings on exposure to a humid environment, with a greater degree of hydrogen-bonding between the polymer and water. Furthermore, morphological changes are then correlated to localised water uptake using the AFM-IR technique. Nanoscale softened regions develop on soaking, and these are found to absorb a greater proportion of water from a humid environment.
Read the full paper on the RSC Publishing portfolio.
2 μm 2 μm AFM-IR maps of the epoxy–phenolic coating after 7 days immersion (a) height and (b) corresponding AFM-IR frequency map gathered under raised humidity at 2964 cm-1 illumination; (c) IR ratio image generated from IR amplitude maps at 3420 cm-1 under 60% RH/30% RH and (d) IR ratio image generated from IR amplitude maps at 3296 cm-1 under RH 60%/30% RH. Circled regions are presented as a guide to the eye.
About Professor Stuart Lyon
Professor Stuart Lyon studied metallurgy and materials science at Cambridge University, followed by a PhD in solid-state electrochemistry. After a short spell in industry he joined the Corrosion and Protection Centre at the former UMIST. His research interests include a variety of corrosion science and engineering topics, including corrosion protection and control. He has published around 150 papers and articles, and has a DSc degree for research in atmospheric corrosion.
Stuart Lyon is a former President of the Institute of Corrosion (ICorr) and is currently Managing Director of Correx Ltd, the trading subsidiary of ICorr. He is on the Corrosion Committee of the Institute of Materials Minerals and Mining (IoMMM) and is Editor-in-Chief of Corrosion Science Engineering and Technology, a publication of IoMMM. He is also a member of the Board of Administrators of the European Federation of Corrosion and the World Corrosion Organisation.
AFM-IR with the NanoIR2
The Anasys nanoIR2 is a nanoscale AFM-IR infrared spectrometer, for rich nanoscale IR spectra from a broad range of real world samples.
- AFM-IR for soft materials, including organics, polymers, composites and life sciences
- True, model-free spectroscopic chemical analysis with AFM-IR – not ambiguous material mapping
- Powerful, full-featured AFM with standard imaging modes
AFM-IR overcomes the limitations of existing AFM-based imaging modes that provide ambiguous material contrast. Instead, AFM-IR delivers true chemical identification. AFM-IR absorption spectra are direct measurements of sample absorption, independent of the other complex optical properties of the tip and sample. As such, AFM-IR spectra correlate very well to conventional bulk IR spectra. Highly accurate peak positions enable detailed analysis of band shapes, subtle peak shifts, secondary structure, orientation effects and more. AFM-IR spectra are easily exported to third party chemical libraries (e.g., Bio-RAD’s KnowItAll®) for rapid analysis and identification of unknown chemical components.
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