Alkaline titanium alloys

Similarly, Allen, Alsalim and Wake 45,46 determined that alkaline hydrogen peroxide was the best pretreatment for titanium alloys. This pretreatment was found to preferentially etch the P phase, while also undercutting some of the a grains and redepositing needle-like crystals on the P grains. The very rough surfaces that resulted were found to enhance adhesion by mechanical aspects. 

Titanium alloys are resistant to alkaline media [43]. In most cases, the corrosion rate is low even in boiling solutions, except in boiling potassium hydroxide. In concentrated NaOH and KOH solutions, the corrosion rate increases at temperatures above the boiling point. 

Examples of intergranular cracking [7.49] comprise i) carbon steel in caustic, nitrate, acetate and carbonate icarbonate solutions, ii) low-alloy steels in pure water, iii) stainless steels that are liable to ordinary intergranular corrosion in oxygen-containing water, iv) a-brass in ammonia solutions that cause surface films, v) aluminium alloys in water vapour and humid hydrogen gas, vi) P-titanium alloys in metanol solutions, vii) tempered martensitic stainless steels in chloride solutions and viii) nickel alloys in very pure water and alkaline solutions. 

Detection Methods. — A nickel-titanium alloy electrode for stable and sensitive electrochemical detection of carbohydrates has been reported." Similarly, several copper(II) oxide modified electrodes were highly sensitive for constant-potential amperometric detection of picomole levels of carbohydrates (Glc, Xyl, xylitol) in alkaline solution in flow through systems (anion-exchange h.p.l.c. and flow injection analysis), although problems with day-to lay reproducibility remained to be solved."... 

Like the aluminum alloys mentioned earlier, the titanium alloy surface can be pretreated by an anodizing process in which there is a controlled rate of surface dissolution accompanied by new oxide formation. Anodizing in bath solutions of either a chromic acid-fluoride or an alkaline-peroxide mixture produces joints with both high initial joint strength and long-term durability. 

Panels of Ti-6-4 alloy adherend were obtained from the NASA-Langley Research Center. The panels were either used in the as-received condition or cleaned by the Pasa-Jell 107 method, a commercial process (American Cyanamid ) for cleaning titanium alloy surfaces. The primary steps in this cleaning process are, briefly sample immersion in degreasing 1,2-Tdichloroethane immersion in an alkaline cleaner, SPREX AN 9 solution pickling in an HNO3/HF solution and treatment with Pasa-Jell 107 (a chromate based acid paste). 

Eigure 21 SEM micrographs of alkaline peroxide etched titanium alloy [25] (Courtesy ... 

Figure 22 SEM micrograph of alkaline anodised titanium alloy [62] (Courtesy Elsevier...

Nickel—Copper. In the soHd state, nickel and copper form a continuous soHd solution. The nickel-rich, nickel—copper alloys are characterized by a good compromise of strength and ductihty and are resistant to corrosion and stress corrosion ia many environments, ia particular water and seawater, nonoxidizing acids, neutral and alkaline salts, and alkaUes. These alloys are weldable and are characterized by elevated and high temperature mechanical properties for certain appHcations. The copper content ia these alloys also easure improved thermal coaductivity for heat exchange. MONEL alloy 400 is a typical nickel-rich, nickel—copper alloy ia which the nickel content is ca 66 wt %. MONEL alloy K-500 is essentially alloy 400 with small additions of aluminum and titanium. Aging of alloy K-500 results in very fine y -precipitates and increased strength (see also Copper alloys). 

Pla.tinum, Platinum plating has found appHcation in the production of platinised titanium, niobium, or tantalum anodes which are used as insoluble anodes in many other plating solutions (see Metalanodes). Plating solutions were often based on platinum "P" salt, which is diamminedinitroplatiniim (IT). A dinitroplatinite sulfate—sulfuric acid bath has been used to plate direcdy onto titanium (129). This bath contains 5 g/L of the platinum salt, pH adjusted to 2.0 with sulfuric acid. The bath is operated at 40°C at 10—100 A/m. Other baths based on chloroplatinic acid have been used in both acid and alkaline formulations the acid bath uses 20 g/L of the platinum salt and 300 g/L hydrochloric acid at 65° C and 10—200 A/m. The alkaline bath uses 10 g/L of the platinum salt, 60 g/L of ammonium phosphate and ammonium hydroxide to give a pH of 2.5—9.0. The alkaline bath can be plated directly onto nickel-base alloys acid baths require a gold strike on most metals. 

A mercury cathode finds widespread application for separations by constant current electrolysis. The most important use is the separation of the alkali and alkaline-earth metals, Al, Be, Mg, Ta, V, Zr, W, U, and the lanthanides from such elements as Fe, Cr, Ni, Co, Zn, Mo, Cd, Cu, Sn, Bi, Ag, Ge, Pd, Pt, Au, Rh, Ir, and Tl, which can, under suitable conditions, be deposited on a mercury cathode. The method is therefore of particular value for the determination of Al, etc., in steels and alloys it is also applied in the separation of iron from such elements as titanium, vanadium, and uranium. In an uncontrolled constant-current electrolysis in an acid medium the cathode potential is limited by the potential at which hydrogen ion is reduced the overpotential of hydrogen on mercury is high (about 0.8 volt), and consequently more metals are deposited from an acid solution at a mercury cathode than with a platinum cathode.10... 

Other metals, such as copper, nickel, or silver, have been used as electrode materials in connection with specific applications, such as the detection of amino acids or carbohydrates in alkaline media (copper and nickel) and cyanide or sulfur compounds (silver). Unlike platinum or gold electrodes, these electrodes offer a stable response for carbohydrates at constant potentials, through the formation of high-valence oxyhydroxide species formed in situ on the surface and believed to act as redox mediators (40,41). Bismuth film electrodes (preplated or in situ plated ones) have been shown to be an attractive alternative to mercury films used for stripping voltammetry of trace metals (42,43). Alloy electrodes (e.g., platinum-ruthenium, nickel-titanium) are also being used for addressing adsorption or corrosion effects of one of their components. The bifunctional catalytic mechanism of alloy electrodes (such as Pt-Ru or Pt-Sn ones) has been particularly useful for fuel cell applications (44). 

W-lOTi alloy targets are produced by blending ultrapure tungsten (see also Section 5.7.6) and titanium powders (obtained by vacuum melting and subsequent pulverizing), followed by pressure sintering. The impurity level has to be very low, in particular, with respect to radioactive elements (U, Th) and mobile alkaline metals (Na, K). 

The indophenol method has been applied for determination of nitrogen (as ammonia) in biological materials [31,32], plant materials [33,34], foods [1,2,35], air [36], boiler water [37], and other waters [38-40], organic substances [17,41], refractory alloys [42], tantalum alloys [43], vanadium, titanium, and uranium [21], alkali and alkaline earth metals [22],... 

ARCTON (75-46-7) Violent reaction with alkaline earth and alkali metals. Reacts violently with aluminum oxide at elevated temperatures, producing hydrogen chloride and phosgene vapors. Incompatible with beryllium, decaborane, diborane, difluoromethylene dihypofluorite, fluorine, lithium, magnesium, potassium, potassium acetylene-1,2-dioxide, potassium acetylene-1,2-dioxide, potassium sodium alloy, sodium amide, titanium, uranium hydride, zinc. Attacks aluminum, magnesium, zinc, and their alloys. 

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