Jct Coatingstech 

Abstract: In Parts 1 1 and 2 2 of this Series, we discussed the technology of applying electrochemical impedance spectroscopy (EIS) to organic coatings on a metallic substrate such as aircraft, marine, or industrial maintenance coatings. This article describes several experimental protocols to evaluate these coatings with EIS. These experimental protocols differ primarily in the process used to stress the coating and accelerate the degradation of the coating. There is no standard recipe for an EIS-based evaluation program that is guaranteed to work for every coating in every environment. This may come in time and, indeed, a standard for EIS evaluation of coatings is under development at ASTM and JSO. 3 However, EIS can be employed in a variety of ways to evaluate virtually any coating. It may be useful to think of EIS as a very sensitive detector that provides a snapshot of coating status. However, a single EIS measurement of an organic coating tells you nothing. To measure coating lifetime or performance, the coating must be stressed to bring about its failure. By making periodic EIS measurements during the stress process, a rate of coating failure can be estimated and a series of coatings may be ranked. Even though some publications discuss the determination of the time-to-failure of a coating, this may be an unrealistic goal. There are too many variables that separate us from this "Holy Grail," most of which are not related to EIS. A more achievable objective is to use EIS in an experimental program that results in a performance ranking of a series of coatings for use in a specific environment. The nature of the stress applied to the coating is, of course, very important in several aspects. The experimental design to prompt the failure of the coating must (1) simulate the service environment the coating will encounter and (2) it must not change the failure mechanism.4 To use EIS to evaluate a specific coating system, (1) place the coated sample in an environment designed to accelerate the degradation of the coating, (2) measure the EIS curves over time, and (3) identify an "index" that tracks coating quality. The index could be the Coatings Capacitance or the Pore Resistance, for example. The index can be very simple or more complex and we will look at several examples in this article. Unfortunately, all coatings do not fail in the same way, so there is no universal index for assessing coating quality with EIS. This complex nature of coatings is no surprise to coatings scientists. A coating system may consist of the metal substrate, surface pretreatment, a primer, and one or more topcoats. Results can vary depending on types of coatings, thickness, number of layers, surface treatment, and the nature of the metal substrate.

Abstract: Nanomaterial technology is receiving a great deal of attention in the coatings industry today. Several approaches within this technology can be used to achieve organic-inorganic nanocomposite or nanostructured coatings. These approaches include incorporation of preformed nanoparticles in organic resin systems, in-situ generation of nanoparticles or nanophases, and other nanostructuring mechanisms. Following an overview of benefits and critical issues of nanomaterial technology, this article reviews advancements in the application of nanomaterial technology to coatings. Several commercial applications of the technology are described.

Abstract: Fluorine polymers, commonly referred to as fluoropolymers, can greatly enhance the properties of coatings used in modern industrial, household, and construction products. The qualities of fluoropolymer resins and oligomeric additives make them an ideal solution for applications requiring a high resistance to solvents, acids, and bases, and-most importantly-an ability to significantly reduce friction. 1 Such surfactant additives reduce surface energy while increasing chemical, UV, moisture, grease and dirt resistance, and surface lubricity. In addition to more common fluorinated olefin-based polymers, specialty fluoroacrylates, fluorosilicone acrylates, fluorourethanes, and perfluoropolyethers/perfluoropolyoxetanes have been found to exhibit properties of interest for coatings applications. Many of these new products are designed to address the concerns about perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) associated with many existing fluoropolymer chemistries. Coatings containing fluorochemicals find applications in electronics (photomask covers, anti-reflection coatings), construction (highly protective coatings for exterior substrates), cool-roof coatings, and optics (antifouling coatings for eyeglass lenses and liquid crystal displays). Other general coatings that may contain fluoropolymers include floor polishes, wood stains, automotive clearcoats, as well as ink jet inks, pigment dispersions, and adhesives. In this article, we will review the properties of fluorochemicals and their numerous variations. We will also analyze current uses and technical applications, and how they might be utilized differently for future coatings applications.