Zinc Phosphating—Immersion

Granodixing Process, developed by the American Chemical Paint Co, Waterbury, Conn for rust prevention of iron, steel, zinc or cadmium consists in immersing the material in a hot soln of acid zinc phosphate. This operation forms an acid resistant coating. The resulting material may be painted... 

All of the coating was carried out on 3 inch X 5 inch, 24-gage zinc-phosphated (Bonderite EP-2), cold rolled steel panels with a deionized rinse. Each panel was immersed in the electrodeposition bath to a constant depth of 10 cm so that a current density or 2.0 ma/cm2 could be used for all coating experiments. 

Phosphating A steel object is immersed in a bath containing zinc phosphate and phosphoric acid to precipitate zinc phosphate on the surface. 

The tissue blocks were immersed in 0.1 M phosphate buffer containing 2% glutaraldehyde and 5% sucrose (pH 7.4). The tissue blocks were immersed in ZIO solution. The ZIO solution was prepared as follows 3 g of zinc (powder) was dissolved ultrasonically in 20 mL distilled water and 1 g of iodine crystals was slowly added to the zinc suspension with stirring. After cooling, 4 mL of the filtered solution was mixed with 2 mL of Tris-HCl buffer (pH 7.5) and 2 mL of 2% Os04 solution. Treatment with this ZIO mixture was carried out for 16-20 h at 4°C in the dark. 

One of the best finishes for firearm steel is phosphatizing (Parkerizing) but few manufacturers offer this finish other than if required for military or police markets. The process deposits a crystalline layer of phosphates on the metal surface by immersion in a bath of iron, zinc, or manganese dioxide and phosphoric acid. Of these, a manganese phosphate finish is preferred for military use. 

Phosphating provides a corrosion-resistant undercoat for paint finishes on steel (particularly automotive bodies), and to a lesser extent on zinc and aluminium. The usual process consists of immersion in a bath containing phosphoric acid, a metal phosphate (usually iron or zinc), and an accelerator, the pH varying between 1.8 and 3.2, at 60-90°C. 

It is also used for the manufacture of soluble phosphate fertilizers (Chap. 21), of ammonium sulfate for use as a fertilizer, of other sulfates, and in the manufacture of many chemicals and drugs. Steel is usually cleaned of iron rust (is pickled ) by immersion in a bath of sulfuric acid before it is coated with zinc, tin, or enamel. The use of sulfuric acid as the electrolyte in ordinary storage cells has been mentioned (Chap. 14). 

Addition of compounds with appropriate functionality to serve as nucleation sites for calcium phosphate growth to polymers can potentially improve the biocompatibility of the latter and thus the long-term stability of implant devices (Drelich and Field, 2007). Zinc stearate was added to poly(ethylene) to form poly(ethylene)-stearate blends with increased surface porosity potentially able to improve mechanical stability of the implant through enhanced osseointegration, improved rates and quality of bone-implant fusion and enhanced soft tissue wound healing via stimulation of angiogenesis. While immersion of these blends in supersaturated calcium phosphate solutions triggered deposition of a porous layer, the deposition rate was very slow, around 100 nm/day. 

Figure 10a. SEM photomicrograph of copper-2% zinc alloy exposed for 4 h in 11.6 g/L y-globulin phosphated saline solution at 25°, pH 7.4, by immersion only.

Figures 12a-d present the surface appearances of copper-2% zinc alloy exposed to the phosphated-saline albumin-globulin-fibrinogen solution. The as-immersed surface (Figures 12a-b) exhibited a protein layer, protein accumulation, and copper chloride phosphates as corrosion products. Polarization at —0.3 V eliminated the outer surfaces of protein accumulation and of corrosion products. Only the underlying protein layer was observed (Figure 11c). Polarization at -0.5 V desorbed most of the protein (Figure lid).

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