White, corrosion

Taghabue closed cup (TCC) unless otherwise noted. Red is flammable white, corrosive. 

Calcium carbonate has normal pH and inverse temperature solubilities. Hence, such deposits readily form as pH and water temperature rise. Copper carbonate can form beneath deposit accumulations, producing a friable bluish-white corrosion product (Fig. 4.17). Beneath the carbonate, sparkling, ruby-red cuprous oxide crystals will often be found on copper alloys (Fig. 4.18). The cuprous oxide is friable, as these crystals are small and do not readily cling to one another or other surfaces (Fig. 4.19). If chloride concentrations are high, a white copper chloride corrosion product may be present beneath the cuprous oxide layer. However, experience shows that copper chloride accumulation is usually slight relative to other corrosion product masses in most natural waters. 

The internal surface was generally covered with dark, tenacious corrosion products. Traces of greenish-white corrosion product were also present. Many small, intersecting pits pockmarked internal surfaces. Thinning was pronounced near the failure where the remaining metal was paper thin. 

White, friable corrosion products composed of Bayerite AI2O3 3H2O, caustic, and NaA102 cover corroded areas (Fig. 8.3). The white corrosion product and deposit usually test as distinctly alkaline when mixed with distilled water. Corrosion products usually cling tenaciously to the underl3dng metal and do not form voluminous lumps. Instead, corrosion products line and coat generally wasted surfaces below. 

Under these circumstances the metal s surface within the crevice became active and it corroded with the formation of a yellowish-white corrosion product that was identified as being mainly rutile TiOj. On the other hand, a Ti-0- 13Pd alloy was found to be immune from crevice corrosion, since the presence of the palladium facilitated passivation of the metal surfaces forming the crevice. 

In areas near the sea coast the rates of corrosion may be increased somewhat by the sea spray containing soluble chlorides, but the rates are still much lower than those prevailing in heavily polluted industrial areas. The white corrosion product which is sometimes found under these conditions probably consists of the basic chloride Zn20Cl2 . 

Sodium, acid sulfite or sodium hydrogen sulfite (NaHS03) has a MW of 104 and a sp. gr. of 1.48. It is a white, corrosive crystalline powder that is very soluble in hot or cold water. It is approved in the United States under 21CFR 173.310, GRAS. It is typically available as a 40% w/w... 

Sodium hydroxide, NaOH, is a soft, waxy, white, corrosive solid that is sold commercially as lye. It is an important industrial chemical because it is an inexpensive starting material for the production of other sodium salts. The amount of electricity used to electrolyze brine to produce NaOH in the chloralkali process (Section 12.13) is second only to the amount used to extract aluminum from its ores. The process produces chlorine and hydrogen gases as well as aqueous socFinn hydroxide (Fig. 14.17). The net ionic equation for the reaction is... 

For zinc deposits, various chromates can produce very thin, blue-bright coatings to get up to about 24 hours salt spray protection before the zinc corrodes (white corrosion salts), thicker yellow iridescent films for up to about 100 hours, and thickest, olive-drab coatings that may give upward of 300 hours (160). A modification of the olive-drab chromate solution with a silver salt produces a black finish, but salt spray resistance drops back to 48—72 hours. Topcoats of waxes are often used on such blacks. Higher salt spray resistance is being claimed for chromates on the zinc alloys eg, 250 hours for... 

It can be seen that the bulge was caused by the formation of a white corrosion product on the outer surface of the aluminum extrusion. This voluminous material, trapped between the copper and the aluminum, exerted pressure on the relatively soft copper sheet, causing it to deform. 

Traffic signs, streetlamp standards, metal barriers and fences, and many other items seen along roads are usually manufactured in galvanized steel (normal mild steel with a zinc coating). On such items it is common to see white corrosion (zinc oxide), characteristic of the oxidation of a zinc coating, often with spots of red rust also appearing that indicate that the steel base is being corroded. 

Pale yellow, volatile solid. Highly poisonousI Very corrosive to sktnl mp 32.1° bp 45.9". Also reported mp 33.4 bp 47.5", Cady, Hargreaves, J. Chem. Soc. 1961, 1563. Hydrolyzed oti exposure to moisture forms white corrosive fumes which soon turn bluish. May be stored in quartz ampuls. 

P. Arora, B.N. Popov, B.S. Haran, M. Rama, S.N. Popova, R.E. White, Corrosion initiation time of steel reinforcement in a chloride environment a one dimensional solution, Corros. Sci. 39 (1997) 739-757. 

White rust (ca. 1848) n. White corrosion products (zinc hydroxide and zinc oxide) on zinc-coated articles. They form when the parts are stored so close together that condensed moisture is entrapped between them and the air circulation is inadequate to assist drying. Baboian R (2002) Corrosion engineer s handbook, 3rd edn. NACE International - The Corrosion Society, Houston, TX. 

Galvanized steel. Galvanized steel must be cleaned to remove the oil or wax that is applied at the mill to prevent white corrosion. After cleaning, the surfaces are pretreated using chromates and phosphates. Vinyl wash primer pretreatments can also be applied on galvanized steel surfaces having no other pretreatments. 

This point was considerably amplified by Carter (1972), who refers to comments by Sample in a paper on the use and misuse of salt spray testing in which he also pointed out that a plentiful supply of well conducting electrolyte could lead to erroneous results by comparison with atmospheric exposure where there is alternate wetting and drying by a poorly conducting electrolyte. In such a case there is an acceleration of the yield of the voluminous white corrosion products that appear on zinc and can cause zinc to have a poor rating from some organizations. 

Very favorable but unsound comparisons can be made for zinc-rich paints as related to metallic zinc coatings by use of accelerated tests because the binder in the paint delays the onset of formation of white corrosion products, whereas in practice, the performance is related to the amount of zinc present and to the general formulation rather than to the initially exposed surface. 

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