The aim of the present article is to review some of the common corrosion phenomena and describe the predominant corrosion mechanisms in high-temperature and supercritical water. Corrosion in aqueous systems up to supercritical temperatures is determined by several solution-dependent and material-dependent factors. Solution-depending factors are the density, the temperature, the pH value, and the electrochemical potential of the solution, and the aggressiveness of the attacking anions. Material-dependent parameters include alloy composition, surface condition, material purity, and heat treatment. Corrosion phenomena that are observed include intergranular corrosion, pitting, general corrosion, and stress corrosion cracking. The solubility and dissociation of both attacking species and corrosion products play the most important role for corrosion in high-temperature water. Both solubility and dissociation processes are strongly influenced by the density, or the ionic product, respectively, of the solvent. High values of both parameters favor ionic reactions, and thus, accelerate electrochemical forms of corrosion. At low densities, water behaves like a non-polar solvent, and thus, ions associate. In these cases, the concentation of e.g. aggressive H + drops down and thus, solutions containing species such as HCl become neutral and thus less aggressive. Further, corrosion products plug the surface and material loss stops. Materials parameters have influence especially on the initiation of corrosion. In the present article, these factors are linked with the physical and chemical properties of high-temperature and supercritical water. An outlook is also given for future research needs.

Corrosion in high-temperature and supercritical water and aqueous solutions: a review

https://works.bepress.com/ram_mohan/12/download/

Applications of bismuth(III) compounds in organic synthesis

Tellurium in Organic Synthesis

Catalytic glycosylation has been a central reaction in carbohydrate chemistry since its introduction by Fischer 125 years ago, but it is only in the past three to four decades that catalytic methods for synthesizing oligosaccharides have appeared. Despite the development of numerous elegant and ingenious catalytic glycosylation methods, only a few are in general use. This review covers all methods of catalytic glycosylation with the focus on the development and application in oligosaccharide synthesis and provide an overview of the scope and limitations of these. The review also includes relevant mechanistic studies of catalytic glycosylations. The future of catalytic glycosylation chemistry is discussed, including specific, upcoming methods and possible directions for the field of research in general.

Catalytic Glycosylations in Oligosaccharide Synthesis

On the development of the electrochemical potentiokinetic method

Optically active myo-inositol 1,4,5-tris(dihydrogen phosphate)1, which has now been recognized as a second messenger in a new intracellular signal transduction system, has been prepared starting from myo-inositol. The key step, phosphorylation of an adequately protected polyhydroxy derivative, was accomplished by three methods, among which a phosphoramidite method using a new phos-phitylating agent, o-xylylene N,N-diethylphosphoramidite, gave the triphosphoric ester in quantitative yield. Optical resolution was effectively realized by derivatization into diastereoisomeric l-menthoxyacetic esters. NMR spectra and optical rotation are shown to depend on the pH of an aqueous solution of compound 1.

Synthesis and some properties of D-myo-inositol 1,4,5-tris(dihydrogen phosphate)

Electrochemical noise behavior of Type 304 austenitic stainless steel (UNS S30400) with various degrees of sensitization was investigated under slow strain rate tensile (SSRT) conditions i...

Current and Potential Fluctuation Characteristics in Intergranular Stress Corrosion Cracking Processes of Stainless Steels

A short and practial synthesis of myo-inositol 1,3,4,5-tetraki(phosphate) and myo-inositol 1,4,5-tris(phosphate) has been achieved by direct benzoylation of myo-inositol, enantioselective tartaroylation and removal of acyl protecting groups with Grignard reagents.

A short step synthesis of optically active myo-inositol 1,3,4,5-tetraki(phosphate) and myo-inositol 1,4,5-tris(phosphate) from 1,3,5-tri-O-benzoyl-myo-inositol

The nondestructive evaluation procedure for detecting in-service materials degradation of low-alloy 2.25Cr-1Mo and CrMoV steels by the electrochemical method has been investigated. The results can be summarized as follows. (1) For 2.25Cr-1Mo steels, the peak current mainly caused by the selective dissolution of coarse carbides M6C appears at ∼+100 mV during potentiodynamic polarization measurements in dilute sodium molybdate solution. This peak value of current density, ΔIp, can be chosen as a reflective parameter of an amount of coarse carbides M6C and shows excellent correlations both with shifts in fracture appearance transition temperature (FATT) caused by carbide coarsening and with hardness change. Actual operational temperature can be estimated from operational period, since the Larson-Miller time-temperature parameter (LMP) value of materials has a unique relationship with ΔIp values. (2) For CrMoV steels, the evaluation of temper embrittlement of CrMoV cast steel by a novel electrochemical technique is described. Intergranular corrosion (IGC) occurs only on temper-embrittled samples during anodic polarization process in calcium nitrate solution. The characteristic changes in polarization curves attributed to IGC have an excellent correlation with shifts in FATT caused by temper embrittlement.

Yutaka Watanabe

Papers

Synthesis and some properties of D-myo-inositol 1,4,5-tris(dihydrogen phosphate)

Current and Potential Fluctuation Characteristics in Intergranular Stress Corrosion Cracking Processes of Stainless Steels

A short step synthesis of optically active myo-inositol 1,3,4,5-tetraki(phosphate) and myo-inositol 1,4,5-tris(phosphate) from 1,3,5-tri-O-benzoyl-myo-inositol

The evaluation of in-service materials degradation of low-alloy steels by the electrochemical method

Glycosylation based on phosphite chemistry