Protective Coating Systems Research Articles

Detection of in Situ Early Corrosion on Polymer-Coated Metal Substrates.

Protective coating systems (PCS) are a common and facile method to protect metal substrates from corrosion. The corrosion control performance of polymer-coated metal substrates is still predominantly evaluated by visual assessment. Unfortunately, for many decades, PCS material development and performance testing has basically been a complicated process of waiting to determine which coating, in relative terms, allows corrosion to occur first from an intentionally created breach through the coating. This type of testing provides only relative ratings between PCS performance. Electrochemical methods, such as electrochemical impedance spectroscopy, each have caveats and pitfalls for qualifying or quantifying polymer-coated metal substrates. When these data are studied carefully, these measurements result in many false positive and false negative results compared with real environmental testing and the paths to failure vary dramatically. The critical issue is that these methods do not result in a scientific basis for understanding either the pathway(s) or progressive milestones toward diminished PCS performance, failure, and the loss of substrate structural integrity for coated substrates. Data supports that ultimately all PCS fail to provide the necessary substrate protection. However, to make substantive gains, scientists and engineers require a rational basis to design, engineer, test, quantify, and/or estimate service life and remaining service life and repair future generations of PCS. Our research goal was to establish a quantifiable characterization protocol (CP) that directly detected, monitored, and ideally quantified the pathway(s) and important milestones of PCS corrosion spatially and temporally, with or without defects which related with testing and assessment variables regardless of environmental severity (real, laboratory, or accelerated). We report herein the CP and the results from an embedded pH-sensitive "turn-on" fluorescent probe blended with a simplified thermoplastic model PCS. The results support that the average-localized macroscopic pH is detected and tracked, and these "molecular titrations" result in values consistent with literature pH citations for premacroscopic corrosion processes, that is, before delamination and a detectable breach. The CPresults are an improvement over visual corrosion detection and yet proportional to the steel substrate corrosion. The CP results deliver extreme early detection (within minutes), spatial and temporal tracking, and potentially quantifiable performance differences for the pathways and milestones toward failure of coated substrates with validated sensitivity to variables such as defect versus defect-free films, blending solvent type(s) influence, differences from varied degrees of annealing relative to Tg (thermoplastic films), substrate topography, and preparation differences. The CP utilizes small sample areas (25 mm spheres) and gathers data in a manner designed to improve statistical relevancy, provide results within short timeframes using real-time testing, diminish materials-testing timelines, and connect results with laboratory, accelerated, and real environmental severity differences. The results support that the CP directly measured the earliest possible in situ corrosion processes using defect and defect-free simplified model PCS.

Concrete Damage in Field Conditions and Protective Sealer and Coating Systems

Concrete structures undergo different forms of damage during their service life. The aim of this study is to identify the most common forms of concrete damage in field conditions. A number of concrete elements and structures were visually inspected and the damage was photographed. The damage phenomena covered are delamination, popout, spalling, scaling, drying shrinkage cracking, corrosion-induced cracking, map cracking, rust and salt stains, discoloration, and mold and moss growths. The probable reasons for these damage phenomena are discussed in this study. Moreover, this study highlights how concrete structures can be protected from the aforementioned forms of damage by using sealer and coating systems as surface treatments. Different sealer and coating systems, emphasizing their selection for specific uses, installation on concrete substrate, effects on concrete durability, performance criteria, and performance evaluation methods have been discussed. Furthermore, some recommendations are given to improve the performance of concrete sealer and coating systems for the protection of concrete structures in field conditions.

Analysis and Alternate Selection of Nanopowder Modifiers to Improve a Special Protective Coating System

This paper presents a practical approach for rational choice of silica nanopowders as modifiers to control and improve the performance of protective coating systems operating in harsh environmental conditions. The approach is based on the multiparameter analysis of nanoparticle reactivity of similar silica synthesized by using chemical and physical methods. The analysis indicates distinct adsorption centers due to the differences in the particles formation; the features of the formation and adsorption mechanisms lead to higher diffusion capacity of the nanoparticles, synthesized by physical methods, into a paint material and finally result in stronger chemical bonds between the system elements. The approach allows reducing the consumption of paint materials by 30% or more, at least 2-3 times increasing of the coating adhesion and hence the system life. Validity of the approach is illustrated through the data obtained from comparative modeling, factory testing, and practical use of modified systems.

Evaluation of long-term corrosion durability and self-healing ability of scratched coating systems on carbon steel in a marine environment

Defects in protective-coating systems on steel surfaces are inevitable in practical engineering applications. A composite coating system, including a primer, middle coat and topcoat, were used to protect carbon steel from corrosion in a marine environment. Two environmental additives, glass fibers and thiourea, were applied in the middle coat to modify the coating system. The long-term corrosion durability and self-healing ability of the scratched coating system were evaluated by multiple methods. Results of the electrochemical technologies indicated that the coating system that contained 0.5 wt.% fibers and 0.5 wt.% thiourea presented good corrosion protection and self-healing for carbon steel when immersed in 3.5% NaCl for 120 d. Evolution of localized corrosion factors with time, as obtained from the current distribution showed that fibers combined with thiourea could inhibit the occurrence of local corrosion in scratched coating systems and retarded the corrosion development significantly. Surface characterization suggested that adequate thiourea could be absorbed uniformly on fibers for a long time to play an important role in protecting the carbon steel. Finally, schematic models were established to demonstrate the action of fibers and thiourea on the exposed surface of the carbon steel and the scratched coating system in the entire deterioration process.

Technological Archives of R & D Activities about Corrosion-Resistant Materials and Protective Coating Systems at High Temperatures in Japan - Historical Retrospection and Future Prospect -

In order to search for the future technological strategy about the high-temperature materials including the coating systems with superior environmental performance, historical archives have been made on the research reports of the JSPS 123rd Committee; about Heat-Resisting Materials and Alloys, for more than 50 years. According to the historical and economic backgrounds associated with a variety of the fuel utilization, the environment-resistant materials have been developed to apply skillfully against different kinds of aggressive environments. Furthermore, future prospects of the corrosion-resistant materials and coating systems were attempted from the viewpoints of both the global environment protection and the energy saving and/or new energy development which must contribute for a prevention of the global warming.

Nanostructured Protective Coating Systems, Fireproof and Environmentally Friendly, Suitable for the Protection of Metallic Substrates

The aim of this study was to formulate, develop, and determine the behavior of nanostructured protective coating systems, fireproof and environmentally friendly, suitable for the protection of metallic substrates. The results allowed concluding that the di- and tripigmented formulations based on laminar zinc, either alone or mixed with nanozinc, showed an excellent corrosion resistance when a nanostructured self-cured inorganic silicate (high silica/alkali ratio) was selected as the film forming material. Coating systems included a sealer of low permeability, which was based on the same film forming material that primers and on laminar pigments. Intumescent coatings were manufactured and then applied on the sealer; in this study, two types of products in an aqueous single package were formulated. The anticorrosive capacity was evaluated in a salt spraying (fog) chamber and in a 100% relative humidity cabinet while the performance against the fire action was determined by estimating the limiting oxygen ind...

X線光電子分光法による防食塗装系の劣化評価

X線光電子分光法による防食塗装系の劣化評価

Testing of Coal Tar Coatings (4) – Surface Preparation And Atmospheric Exposure

Abstract Discusses necessity of specifying non-bituminous inhibitory pigmented primers for all applications of coal tar protective coating-systems. Describes tests in which selected primers and coal tar coatings were applied to coke plant areas subject to high atmospheric corrosivity. All systems applied to wire-brushed surfaces, primed or unprimed, failed within one year. The same systems on sandblasted surfaces, with and without primers, are still in satisfactory condition after five years' exposure in the same environment. Coated panels have been exposed for about four years at Ingleside, Texas, Kure Beach, N. C., and Kearny, N. J. Contrary to expectation, some coatings are weathering faster at Ingleside than at Kearny. Some non-bituminous systems which have already failed in Texas are still in satisfactory condition in New Jersey. Results to date confirm the advisability of specifying coal tar pitch emulsion as the best top coat for coal tar protective coating systems subject to atmospheric exposure. 5.4.5

Topic of the month—Preliminary Evaluation of Protective Coating Systems

Topic of the month—Preliminary Evaluation of Protective Coating Systems