NOPR Collection:

The Dead Sea—A live pool of chemicals

Tue, 01 Jan 2002 00:00:00 GMT

Title: The Dead Sea—A live pool of chemicals Authors: Wisniak, Jaime Abstract: The Dead Sea has been a source of chemicals since ancient times. Large scale production of potash by solar evaporation started in 1931 and today the Dead Sea is intensively exploited by Israel and Jordan as a major source of potash, bromine, and magnesium, for agriculture and the chemical and automotive industries. A smart coupling of solar evaporation and knowledge of the complex phase diagram allows a one-to-one easy separation of the principal salts present in the brine. A description of the properties of the Dead Sea is provided together with a chemical engineering analysis of the processes used to realize its commercial potential. Page(s): 79-87

Mild steel deterioration with time in various aqueous salt solutions

Tue, 01 Jan 2002 00:00:00 GMT

Title: Mild steel deterioration with time in various aqueous salt solutions Authors: Mehra, Rita; Soni, Aditi Abstract: The corrosivity of water supplies need to be evaluated in view of the aesthetic problems in water and also because of the potential public health importance. As such, some recent work on mild steel deterioration has been carried out. The results assessed from weight loss measurements for different chemical mediums support the chloride aggressiveness reported in literature. But the relative behaviour of other ions vary with time being lesser in concentration as per potable water quality standards. Potentiostatic polarisation results have also been carried out to determine the effect of different anions and time on corrosion rate through changes in potential. The corrosion potential (E_corr·), corrosion current (I_corr·), Tafel slopes, corrosion rate have been obtained from polarisation experiments using a three electrode set-up. For reliability of results, the data has been statistically analysed. Page(s): 74-78

Influence of anions on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions in the presence of p-tolyl thiourea

Tue, 01 Jan 2002 00:00:00 GMT

Title: Influence of anions on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions in the presence of p-tolyl thiourea Authors: Muralidharan, S; Madhavan, K; Karthikeyan, S; Iyer, S Venkatakrishna Abstract: The influence of anions such as chloride and sulphate on the inhibition of corrosion of mild steel by p-tolyl thiourea (PTTU) in 1N HCl and 1N H₂SO₄ has been studied using weight loss and gasometric measurements, Galvanostatic polarisation studies and ac impedance measurements. The compound is found to be less inhibitive in 1N HCl than in 1 N H₂SO₄. The influence of p-tolyl thiourea on the extent of hydrogen permeated through mild steel in acidic solutions has been studied using electro-permeation technique. The compound is found to enhance the permeation of hydrogen through mild steel in both the acids. The adsorption of p-tolyl thiourea on the mild steel surface from both the acids obeys Temkin's adsorption isotherm. The increase of charge transfer resistance (R_t) and decrease in double layer capacitance (C_d1) values of the metal electrode in the presence of the test compound (PTTU) show the adsorption of the compound on the metal surface. Page(s): 68-73

Synthesis and dissolution of chromium substituted magnetites in V(II)-EDTA formulation

Tue, 01 Jan 2002 00:00:00 GMT

Title: Synthesis and dissolution of chromium substituted magnetites in V(II)-EDTA formulation Authors: Manjanna, J; Venkateswaran, G; Sherigara, B S; Nayak, P V Abstract: Chemical cleaning or scale removal of boilers, heat exchangers etc., involves the dissolution of metal oxides, which are corrosion products from the base metal. Iron oxides mainly hematites and magnetites are commonly found in the case of Fe based alloys due to corrosion. The decontamination of primary system surface of water-cooled nuclear reactors, in particular Pressurized Light Water Reactor (PWR)/ Pressurized Heavy Water Reactor (PHWR) involves the dissolution of iron oxides formed under reducing coolant chemistry environment ca. magnetite type of oxide matrix. Thus in the present study, the dissolution characteristics of Cr-substituted (0-20 at% Cr) magnetites (c.s.m) in V(II)-EDTA formulation at 353±5 K are reported. The oxides employed were prepared synthetically by co-precipitation method, moderately sintered and physic-chemically characterized. The dissolution rate coefficient, k¹ and the percentage of dissolution were determined. The oxidative pre-treatment of these oxides employing viz., AP, NP and HMnO₄ had resulted in improved dissolution. Page(s): 60-67