Organic coatings application techniques

The anodic process can be stopped by applying a coating to the reinforcement that acts as a physical barrier between the steel and the repair mortar. For this purpose only organic coatings, preferably epoxy based, should be used. Protection is entirely based on the barrier between the reinforcement and the mortar, and passivation of steel cannot be achieved because contact with alkaline repair material is prevented. This method should be used to protect depassivated areas of the reinforcement only as a last resort, i. e. when other techniques are not applicable and only for small specific applications [1,4]. It may be used, for instance, when the thickness of the concrete cover is very low and it is impossible to increase it to the proper level, so that the repair material cannot provide durable protection to the embedded steel. 

The technique was successfully applied to monitoring at remote test sites, under computer control and data transmission to the laboratory via modem [133]. Another interesting application is the ranking of organic coatings, based on the principle that a high Rn corresponds to a good performance [134,135]. 

Paints and coating materials frequently contain substances that may be a hazard both to human health and to the environment. This applies particularly to organic solvents, to certain reactive binder constituents, to pigments containing heavy metals, and to some additives. Evaluation of the environmental properties of paints must take into consideration their effects on the atmosphere, water, and the soil, the potential danger to the user, the use of low-residue application techniques, and the suitability for use. The primary concern is to minimize adverse effects in all sectors. 

Powder coatings have been widely accepted in the industrial coating market because they are completely solvent free and show excellent mechanical and physical properties (13). Usually they contain a synthetic binder, a reactive cross-linker, pigments, and several additives to improve flow and other film eharacteristics. Various application techniques have been developed in reeent years. Powder coatings are normally sprayed electrostatically on grounded substrates and are heat-cured thereafter. Because these systems do not contain organic solvents, no emission of organic solvents takes place. However, the need for an oven to melt the resin and start the chemical reactions makes this environmentally friendly process unsuitable for do-it-yourself markets. 

The use of electrochemical impedance spectroscopy (EIS) for the assessment of coatings has been under development for many years now [83]. The first period application of the technique was restricted to the study of the corrosion occurring with poorly protective coatings and coating impedances were evaluated by shape of the Nyquist plots. However, relatively few reports have been published describing results obtained from protective organic coating systems as used commercially [84]. 

Potassium ionisation of desorbed species (K IDS) with mass spectrometric detection is an extremely useful tool for the characterisation of high performance organic coatings. K IDS uses a commercial rapid heating probe to desorb intact molecules which are then ionised by potassium cation attachment. Based upon the molecular ions, which appear as [M]K, coatings components can be qualitatively and quantitatively analysed. In this work K IDS was selected as a method of soft ionisation, (i.e., producing molecular ions) because of its simplicity, wide applicability, low cost and compatibility with the quadrupole mass spectrometer. Simonsick [76] reports the application of K IDS to polymer additives (UV stabilisers and antioxidants), catalysts (organotin), reactive diluents (vernonia oil and aliphatic epoxides) and polyurethane precursors (polyesters and isocyanates). Tikuisis and co-workers [77] also discussed this technique. 

The relative ease of fabrication is another reason for the extensive application of organic coatings. There are a few techniques to apply such organic coatings to medical devices. Typical techniques such as dip-coating, spray-coating, and spin-coating are briefly explained as follows. 

It was claimed that the maximum continuous operating temperature in most chemical environments was 120°C and even 140-150°C in some instances. The major chemical applications were in the form of pipe and tank linings and injection moulded valve and pump parts. Coatings could be applied to metals by means of fluidised bed, water suspension and organic dispersion techniques. 

The vast increase in the application of membranes has expanded our knowledge of fabrication of various types of membrane, such as organic and inorganic membranes. The inorganic membrane is frequently called a ceramic membrane. To fulfil the need of the market, ceramic membranes represent a distinct class of inorganic membrane. There are a few important parameters involved in ceramic membrane materials, in terms of porous structure, chemical composition and shape of the filter in use. In this research, zirconia-coated y-alumina membranes have been developed using the sol-gel technique. 

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