Accelerant coating

Chromium Chromate. Chromium chromate treatment baths are acidic and made up from sources of hexavalent chromium and complex fluoride, fluorosiHcate, fluorozirconate, fluorotitanate, and siHcofluorides. Optional additional components added to accelerate coating rate are free fluoride, ferricyanide, and other metal salts such as barium nitrate. Conversion coating on aluminum precedes by the following reactions (2,3,17) ... 

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. 

The process for the manufacture of ball-grain powder which Olsen and his co-workers have devised 26 combines nicely with Olsen s process for the quick stabilization of nitrocellulose to form a sequence of operations by which a finished powder may be produced more rapidly and more safely than by the usual process. It supplies a convenient means of making up a powder which contains non-volatile solvents throughout the mass of the grains or deterrent or accelerant coatings upon their surface. 

To optimize the electrodeposited coatings, Wang et al. investigated the influence of current density (1-5 mA/cm ), acetic acid concentration, and chitosan concentration on the deposition of the composite chitosan-CaP coatings [120]. Increased current densities of 4-5 mA/cm as compared to 1-2 mA/cm led to an accelerated coating deposition process and more chitosan deposition. Increasing acetic acid (from 0.05 to 0.15 M) and chitosan (from 0.05 to 0.15 g/L) concentrations, however, inhibited CaP deposition. 

Diethyl-1,2-dihydro-1-phenyl-2-propylpyridine accelerator, coatings Amyl acid phosphate accelerator, cold-cure cements Dibutyl xanthogen disulfide accelerator, composites 1-Phenyl-3,3-dimethyl urea accelerator, concrete setting Calcium formate accelerator, cosmetics Sodium persulfate accelerator, CR... 

Figure Bl.17.8. Iron oxide particles coated with 4 nm of Pt in an m-planar magnetron sputter coater (Hennann and Mtiller 1991). Micrographs were taken in a Hitachi S-900 in-lens field emission SEM at 30,000 primary magnification and an acceleration voltage of 30 kV. Image width is 2163 nm.

Aluminum containers are recommended for many appHcations because of the very hard, corrosion-resistant oxide coating. They are deficient in only one respect once the protective skin has been penetrated, aluminum corrosion accelerates. 

Many cellular plastic products are available with different types of protective faces, including composite metal and plastic foils, fiber-reinforced plastic skins, and other coatings. These reduce but do not eliminate the rate of aging. For optimum performance, such membranes must be totally adhered to the foam, and other imperfections such as wrinkles, cuts, holes, and unprotected edges should be avoided because they all contribute to accelerated aging. 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

The bath components for a nitrite—nitrate accelerated bath basic to this conversion coating process are (/) 2inc metal or 2inc oxide dissolved in acid (2) phosphate ions added as phosphoric acid (J) addition of an oxidant such as sodium nitrite and (4) addition of nitric acid. Other oxidants such as peroxide, chlorate, chlorate in combination with nitrate, or an organic nitro compound may also be used. 

---