Water, corrosion perceptions

Water-Waste Interactions. It is appropriate to examine the water-waste interactions first since this is an extension of our previous interests in the high temperature solubility and mass transfer of corrosion products in power plants (2) and our perceptions in this area are therefore well developed. 

Water-soluble Cl significantly improve the protective ability of oil, alkyd, alkyd-styrene and alkyd-nitrocellulose coatings (Fig. 3.41), for example, 3wt% of water-soluble potassium chromate guanidine. Cl has been introduced into the lacquer base, after which a 20-pm-thick single-layer coat has been applied on a plate of low-carbon steel (St 2). The time until the appearance of corrosion traces under the coating has been recorded on exposure to atmosphere at 100% humidity and a temperature of T = 18-25°C. The results presented in Fig. 3.38 prove that the introduction of this Cl has perceptibly improved the anticorrosion properties of lacquer coatings [1]. 

Chem. Descrip. Glycerin-1-allylether CAS 123-34-2 EINECS/ELINCS 204-6204 Uses Can be polymerized into polyesters, polyurethanes, polyacetals, and epoxy resins (hydroxyl group) or with acrylates, methacrylates, or styrene (ilyl group) for prod, of PL) rubber and foam printed circuit boards unsat. polyesters used for radiation-resist, coatings copolymers as dispersants for pigments or as corrosion inhibitors Properties Colorless to yish. vise, liq., perceptible odor sol. in water, ethanol, and many org. soivs. dens. 1.07 g/cc vapor pressure 0.004 mbar (20 C) m.p. < C b.p. 245 C (decomp.) flash pt. 135 C pH 7 (5% aq.) 9 /o assay... 

Rain or high relative humidity (which can cause condensation) increases corrosion of zinc that is roughly proportional to the time of wetness in a particular environment. Factors that determine time of wetness have been discussed by Grossman (1978). Temperature generally has only an indirect effect in air the relative humidity usually drops as temperature increases. At humidities exceeding 75%, corrosion rates rise perceptibly. A drop in temperature has the opposite effect. In solutions, reaction rates increase with temperature but—more important—in hot tap water there is a potential reversal between zinc and steel typically between 60 and 90°C, which then limits the benefits of a zinc coating to its barrier effect. In addition, localized pitting may occur, as noted in Section IV (How Zinc Can Protect Steel). 

Handling, Storage, and Precautions corrosive should be handled with caution. It does not fume perceptibly in air, but it is moisture sensitive and is slowly decomposed by water over several hours to give the corresponding silanol. ... 

The quenching rate depends on the thermal exchange between the hot metal and the cold water. For sheet a few millimetres thick, quenching is practically instantaneous. With increasing thickness, the quenching rate in the centre of the metal decreases and may reach values so low that sensitivity to intercrystalline corrosion will be perceptible. 

---