Titanium and Zirconium Corrosion Studies

Abstract

were encountered. Under tank condibions the ycast was subject t o variation or degeneration and yielded substrains which did not produce riboflavin. A larger inoculum was required since this organism did not grow as rapidly as Candida guillieimondiu, Therefore a new medium was developed to obtain vigorous growth in the inoculum phase. The composition of t,his medium was as fo1lon.s: Sucrose 40 grams per liter Defatted soya flour (trypsin 10 grams per liter Calcium carbonate 5 grams per liter digested 2 hours a t 37' C.) Shake flasks containing 100 nil. of this medium ~w r e st>er and inoculated from slants. Owing to the high iron level of this medium no more than 100 ml. could be added to a 23-liter f c~ mentation. This volume of inoculum did not supp cells to combat contaniinati0n; therefore, an intermed inoculum stage was introduced. Six liters of niedimn 4B \vert; sterilized in a bottle fitted with a porous candle aerator and ari air filter. The urea n-as sterilized separately to avoid decomposition. -4fter cooling, the urea was added to the sterile medium and 107' by volume of 24-hour soya medium shake culture was added as inoculum. During 20 to 24 hours' growth at) 30" C. under vigorous aeration, the pH fell from 6.2 to 5.0 or loircr. Five per cent of this culture TWS then used to inoculate 24 liters of nonsterile medium 4B. Using t,his technique, pot,encies as high as 3257 per nil. were obtained, but in some runs the above yields n-ere not obtained for unknown reasons. A summary of data from one experiment involving t,hree tanks using the above technique is given in Figure 2. The curve of riboflaviii production is closely related to the yeast growth curve.I t was felt that a possible csplanat,ion for the occasional failures in the tanks might be due to the sterilized medium used in the secpnd stage of inoculum culture. -4 new technique was developed which eliminated the usc of st>erilc medium. -4 sinal1 volume (1 to 3 liters) of nonsterile medium 413 mas inoculated with 100 ml. of soya medium culture and acratcd as 1x;fore. B s the growth increased, nonsterile medium 4B was added to maintain a constant but high ratio of cells to volume. When a volume of 6 liters was reached (pH 4.0 to 5.5), the entire stagc was used as inoculum for 18 liters of nonsterile medium 4B.Using this procedure, a series of 81 experimental 24-lit,er tanks were run in order to determine the average yield and reproducibility of this method. Of these 81 tanks, 03 ivere not contaniinat,ed, while 16 tanks viere low in potency due to coiitarnination and 2 were low due to the failure of the agitation system. The average riboflavin potency of all t,hc t,anlrs was 1617 per ml.The average potency of the 63 iioncontaminated tanks was 1917 per nil. The distribution of riboflavin yields among these 63 tanks is tabulated below: 01-er 300-, por ml. Between 200 and 3007 per inl. Between 100 and 2 0 0 y per ml.

Corrosion Resistance of Titanium, Zirconium, and Stainless Steel in Organic Compounds

“…The apparatus used in these tests conforms to the recommendations of the American Society for Testing Materials as contained in the Tentative Method of Total Immersion Corrosion Tests of Nonferrous Metals (1). A detailed description of the apparatus is contained in previously published papers (6,8). Aeration was supplied either b>7 compressed air from the laboratory air line, or by cylinder nitrogen.…”

“…The important pollutants of the Los Angeles atmosphere and their concentrations listed in Table I are representative of air sampling data obtained during clear and smog periods (10). Investigations covering these contaminants have led to a number of conclusions regarding the causes of the characteristic haze that often reduces visibility to less than 1 mile (11, IB), the causes of gas damage to vegetation (B, 8, 8), the nature of the eye-irritating materials (6), and the high rate of rubber cracking (6,7). A complete discussion of these experimental studies is beyond the scope of this paper.…”

Resistance of Titanium to Sulfuric and Hydrochloric Acids Inhibited by Ferric and Cupric Ions

“…It is not a durable material, however, when exposed to sulfuric or hydrochloric acids. At 100~ it is reported that 3 per cent HC1 corrodes titanium at a rate of about 1700 mdd (0.5 ipy) (1). Stainless steels of the 18 per cent Cr, 8 per cent Ni variety (18-8) are also attacked by these acids, but, in the case of sulfuric acid, the corrosion rate can be substantially reduced by small additions of ferric or cupric sulfates.…”

A simple one step process for enhancement of titanium foil dye sensitised solar cell anodes

“…For this, cleaned asreceived Ti foils were treated with H 2 O 2 under high reaction rate conditions (high temperature, limited period of time) and low reaction rate conditions (room temperature, long period of time) or the same treatments were carried out on Ti foils previously treated with 30% nitric acid (HNO 3 ), a well-known passivating agent for Ti. 9 Surprisingly, despite an obvious surface area increase with H 2 O 2 treatments, the best performance enhancement of the back-illuminated DSSC was achieved using only the simple HNO 3 treatment. No laborious chemical etching or polishing pre-treatments are necessary.…”