Chromium, surface preparation

Frankenthal, R. P., The Effect of Surface Preparation on Pitting and Anodic Dissolution of Iron-Chromium Alloys , J. Electrochem. Soc., 114, 201c (1967)... 

Table II presents the results of some wettability measurements on adsorbed monolayers prepared from molten Compound D on pure, polished, clean, chromium surfaces after solvent treatment had been used to remove all surplus solidified acid. A series of successive solvent treatments was applied to each coated specimen (see first four columns of Table II) using liquids which have been shown to be good solvents for Compound in the bulk (9). These liquids were either absolute ethyl alcohol or benzene at or above 20°C., or n-hexane at or above 60°C. In the remaining columns are listed the average values of the slowly advancing contact angles measured by the drop-buildup method on from three to five different drops. Measurements were made on sessile drops of water, thiodiglycol, and methylene iodide. These three diagnostic liquids were chosen because of their high surface tensions (72.8, 54.0,...

Welding that may release metal fumes such as those of zinc that can cause a condition of metal fume fever characterized by elevated temperature and chills Painting and coating, especially in surface preparation where cleaning old surfaces may release airborne lead, chromium, or other toxic substances Waste handling that may expose workers to toxic waste materials... 

PHOSPHORIC ACID. H. P04- In laboratory tests, aqueous solutions of phosphoric acid (5-85%) were corrosive to 1100 alloy and the corrosion increased with concentration at ambient temperature. The rate attack was - 100 mpy at 5% and - 1200 mpy at 85% concentration. The action of pho horic acid can be reduced by the addition of inhibitors. Aqueous solutions containing phosphoric acid and chromium trioxide have been used as cleaning solutions and as surface preparation for painting of aluminum alloys. See also Ref (Dp. 139, (2)p. 566, (3)p, 132, (4) pp. 21. 29, 30. 74. 86. 138.139. (7) p. 143. 

Stainless steel, or corrosion-resistant (CRES) steel, has a high chromium content (11% or higher) as the primary alloying element. There have been a large number of surface preparation methods reported in the literature. An excellent report... 

Organochromium Catalysts. Several commercially important catalysts utilize organ ochromium compounds. Some of them are prepared by supporting bis(triphenylsilyl)chromate on siUca or siUca-alumina in a hydrocarbon slurry followed by a treatment with alkyl aluminum compounds (41). Other catalysts are based on bis(cyclopentadienyl)chromium deposited on siUca (42). The reactions between the hydroxyl groups in siUca and the chromium compounds leave various chromium species chemically linked to the siUca surface. The productivity of supported organochromium catalysts is also high, around 8—10 kg PE/g catalyst (800—1000 kg PE/g Cr). 

Chromium carbide is important in powder preparations designed for thermal spray apphcations of corrosion and wear-resistant coatings on tool and machine parts. Lower carbon carbides of chromium are important in hardfacing tods and electrodes for weld-apphed ovedays on machine wear surfaces. However, these carbides are usually formed in situ from Cr and C in the rod and not added as preformed carbides. The properties of Ci2C2 are hsted in Table 2. 

Aqueous standard solutions are a source of certain difficulties In electrothermal atomic absorption spectrometry of trace metals In biological fluids The viscosities and surface tensions of aqueous standard solutions are substantially less than the viscosities and surface tensions of serum, blood and other proteln-contalnlng fluids These factors Introduce volumetric disparities In pipetting of standard solutions and body fluids, and also cause differences In penetration of these liquids Into porous graphite tubes or rods Preliminary treatment of porous graphite with xylene may help to minimize the differences of liquid penetration (53,67) A more satisfactory solution of this problem Is preparation of standards In aqueous solutions of metal-free dextran (50-60 g/llter), as first proposed by Pekarek et al ( ) for the standardization of serum chromium analyses This practice has been used successfully by the present author for standardization of analyses of serum nickel The standard solutions which are prepared In aqueous dextran resemble serum In regard to viscosity and surface tension Introduction of dextran-contalnlng standard solutions Is an Important contribution to electrothermal atomic absorption analysis of trace metals In body fluids. 

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