Dissolution of coatings

Elirsch, S., Binder, V., Kolter, K., Kesselhut, J.F., and Bauer, K.H., Lauroyl dextran as a coating material for site-specific drug delivery to the colon in vitro dissolution of coated tablets, Proc. Int. Symp. Control. Rel. Bioact. Mater., 24 379-380 (1997). 

Fig. 9a, b. TEM images of a a nickel nanorod coated with a titania/PDADMAC coating b tita-nia-based (titania/PDADMAC) nanotubes obtained following dissolution of coated nickel nanorods. The inset shows ahigher magnification of the nanotubes shown in b. (Adapted from [51] by permission of the American Chemical Society)... 

The possible delamination modes are (i) loss of adhesion at paint/phosphate interface, (ii) within phosphate layer due to mechanical fracture (iii) due to dissolution of phosphate (iv) dissolution of coating (v) mechanical failure at coating/steel interface. 

TRCS with the dissolution-induced cell detachment character is reported by Rollason et al. (Rollason et al., 1993) after Okano s and Takezawa s reports (Takezawa et al., 1990 Yamada et al., 1990). Recently, a few reports point out more convenient fabrication of cell sheet from the coated polymer dissolution-based TRCS (Mukundan et al., 2011 Nash et al., 2011 Varghese, Raj, Sreenivasan, Kumary, 2010). Nash et al. have showed that various ceU lines are able to be harvested from PIPAAm homopolymer-coated Thermonox disk surfaces. Cell adhesive character on a PIPAAm homopolymer-coaled disk surface is independent from coated polymer layer thickness. CeU detachment mechanism described in these reports is speculated to be due to the dissolution of coated polymers, as mentioned previously, by Rollason et al. (1993). 

When utilizing a lead-free solder in a wave process, the machine and process must be modified to ensure the alloy selected is compatible with the internal parts of a wave machine. Lead-free solders are not drop in replacements , for eutectic Sn-Pb solder. Issues such as lead contamination, flux chemistry compatibility, dross removal equipment, and dissolution of coatings on the surfaces of a wave machines internal parts into the solder alloy must be considered. 

Other Properties. With respect to dry-cleanabiUty, vinyl-coated fabrics are worse than the others due to dissolution of plasticizer in the cleaning solvent. Only man-made leathers with poromeric nonwoven can be skived, spHt, and cut in the same manner as leather. 

The most significant chemical property of zinc is its high reduction potential. Zinc, which is above iron in the electromotive series, displaces iron ions from solution and prevents dissolution of the iron. For this reason, zinc is used extensively in coating steel, eg, by galvanizing and in zinc dust paints, and as a sacrificial anode in protecting pipelines, ship hulls, etc. 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

Principles Immersion plating resulting from a displacement reaction involving the metal to be coated can continue only as long as the less noble substrate remains accessible to the plating solution, and therefore as plating proceeds, the quantity of A/, deposited, and of A/j dissolved, falls. Dissolution of A/j can be avoided by coupling it with a less noble metal A/, so that only A/j dissolves, i.e, by internal electrolysis. 

Hot Dipped Coatings Major attempts have been made to improve the quality of aluminised steel strip. Requirements on coating thickness and uniformity have been imposed. It is the speed of sheet movement, length of path in the molten bath, temperature and composition of the bath that control the thickness of the intermetallic layer which lies below the aluminium outer surface. The process of intermetallic alloy formation is diffusion controlled, and it is usual that some dissolution of iron into the molten aluminium does occur at a rate, Ac/At, which is given by... 

Even small traces of certain corrosion stimulants, notably soluble chlorides and sulphates, can maintain a continuing corrosion process under a paint film because the salts accelerate the initial dissolution of ferrous iron (and other metal ions) but are not immobilised in the hydrated oxide corrosion products. Filiform corrosion is the most spectacular example of this phenomenon, but progressive spread, preceded by blistering, is also observed from scratches or other breaks in a coating, for example during salt spray tests. 

The solution of iron represented in equation 15.1 takes place at local anodes of the steel being processed, while discharge of hydrogen ions with simultaneous dissociation and deposition of the metal phosphate takes place at the local cathodes. Thus factors which favour the cathode process will accelerate coating formation and conversely factors favouring the dissolution of iron will hinder the process. 

In plain tinplate cans for acid foods, tin provides cathodic protection to steel (3,4). The slow dissolution of tin prevents steel corrosion. Many investigators (5-1I) have defined this mechanism in detail and have shown that the tin dissolution rate is a function of the cathodic activity of the base steel, the steel area exposed through the tin and the tin-iron alloy layers, and the stannous ion concentration. Kamm et al. showed that control of the growth of the tin—iron alloy layer provides a nearly continuous tin-iron alloy layer and improves the corrosion resistance of heavily coated (over 45 X 10"6 in. tin) ETP for mildly acid food products in which tin provides cathodic protection to steel (12). The controlled tin-iron alloy layer reduces the area of steel exposed to the product. ETP with the controlled alloy is designated type K, and since 1964, 75 type K ETP has been used to provide the same protection as 100 ETP provided previously (13). 

Phillips, J. F. Dissolution of Oxide-Coated Zirconium and Zirconium Alloys, U.S. AEC Report BNWL-600, Pacific Northwest Laboratory, Richland, WA, 1968. 

Another method to synthesize hollow nanocapsules involves the use of nanoparticle templates as the core, growing a shell around them, then subsequently removing the core by dissolution [30-32]. Although this approach is reminiscent of the sacrificial core method, the nanoparticles are first trapped and aligned in membrane pores by vacuum filtration rather than coated while in aqueous solution. The nanoparticles are employed as templates for polymer nucleation and growth Polymerization of a conducting polymer around the nanoparticles results in polymer-coated particles and, following dissolution of the core particles, hollow polymer nanocapsules are obtained. 

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