Sodium hydroxide etch

A sodium hydroxide etch process has been developed for polyimide parts that require maximum adhesive strength.53 The parts are first degreased and then etched for 1 min at 60 to 90°C in 5 percent solution of sodium hydroxide in water. After etching, the parts are rinsed in cold water and air-dried. 

Another possibility to use PET recyclate for food applications is the URRC process (United Resource Recovery Corporation). In this method the cleaned PET flakes are covered with concentrated caustic soda. After evaporation of the water in a rotary kiln the sodium hydroxide etches the surface of the PET at a temperature of more than 200°C. The resulting sodium terephthalate is removed by washing. The remaining flakes are used for the production of bottle preforms. Since 2000 several plants in Switzerland and Germany have been established [1],... 

Table 4 Adhesive Tensile Strength Between Sodium Hydroxide-Etched CMP and Monomers Containing Carboxyl Groups in Water...

Fig. 2 Scanning electron micrographs of (a) polished, (b) lactic acid-etched, and (c) sodium hydroxide-etched CMP plate.

Polyamide and polyester fibres are generally scoured using an alkyl poly(oxyethylene) sulphate and sodium carbonate. Some polyester qualities are subjected to a causticisation treatment with sodium hydroxide in the presence of a cationic surfactant to give a lighter fabric with a silkier handle [154,156]. This treatment involves etching (localised saponification) of the polyester surface and is broadly analogous to the S-finish used on triacetate fibres. The process has attracted considerable interest in recent years but its... 

Hydrofluoric Acid. — Evaporate 10 cc. of hydrogen peroxide with a few drops of sodium hydroxide solution, transfer the concentrated liquid to a watch glass, evaporate to dryness on the latter, pour concentrated sulphuric acid over the residue, and allow the whole to stand two to three hours in a warm place. After washing off the glass, no etching should be visible. 

Specialty Chromium-Plating Baths. Chromic acid baths using sodium chromate and sodium hydroxide to form a tetrachromate (92) have had limited use. Porous chromium is used in lubricated wear applications, and is made by chemically etching regular chromium plate, sometimes with light grinding after the etch. Black chromium is used on solar collector surfaces (see PHOTOVOLTAIC CELLS Solarenergy). Baths are sulfate-free, and include fluosilicic acid or acetic acid (91). 

The starting compound for all triazinylaminostilbenes is 4,4 -dinitrostilbene-2,2 -disulfonic acid [128-42-7], which is obtained by oxidizing 4-nitrotoluene-2-sulfonic acid with aqueous sodium hypochlorite in the presence of sodium hydroxide or, more recently, by atmospheric oxidation in an aqueous ammoniacal medium [39], The Bechamps reduction using iron filings etched with hydrochloric acid yields 4,4 -diaminostilbene-2,2 -disulfonic acid [81-11-8] (DAS). 

Fig. 8.14. SEM micrographs of etched ZnO single crystals. The crystals were etched either in hydrochloric acid (top) or in sodium hydroxide solution (bottom). The graph shows the zinc terminated (001) (left) and the oxygen terminated (001) (right) surface after the respective etching step. The angles 7 spanned by the two opposite edges and <5 between the (101) faces of the etch crater are about 130° and 123°, respectively...

ASTM D 2651 sodium hydroxide-chromic acid etch... 

The difficultly soluble sodium salt from the first step is dissolved in 300 cc. hot water, and the free sodium hydroxide present is neutralized with dilute hydrochloric acid. The resulting solution is added during the course of 30 minutes to 200 grams of iron turnings which have been etched with 20 cc. 40 per cent acetic acid. The reduction then proceeds in the normal way (see, e.g., page 75). 

I. Barycka, H. Teterycz, and Z. Znamirowski, Sodium hydroxide solution shows selective etching of boron-doped silicon, J. Electrochem. Soc. 126, 345, 1979. 

Preparation. (a) Aluminum turnings (oil-free) are etched with dilute sodium hydroxide to a point of strong hydrogen evolution, the solution is decanted, and the metal is washed once superficially with water so that it retains some alkali. It is then treated with 0.5% mercuric chloride solution for 1-2 min., and the entire process is repeated. The shiny amalgamated metal is washed rapidly In turn with water,... 

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