Corrosion of aluminium in aliphatic amines and its inhibition by some dyes

Corrosion rates of aluminium alloys 2S, 3S, M57S and B26S in aqueous solutions of aliphatic amines and the inhibition efficiency of some dyes on the corrosion of 3S aluminium in these amines has been studied. The corrosion rate increases with the amine concentration up to 0.1 M and then decreases. The general order of corrosivity of amines is: tertiary < primary < secondary while for ethanolamines, the order is: tri- < di- < monoethanolamine. The order of corrosion susceptibility of different alloys in uninhibited amines M 57S < 2S < B26S < 3S. A rise in temperature increases the corrosion rate of 3S aluminium in 0.1 M amine with the energy of activation having an almost constant value of 48.9 kJ/mol in the temperature range 20–50° C. In 0.1 M methylamine, the inhibiting efficiency of different compounds (concentration 0.1%) increases in the order: alizarin red-S (5.8%) < fluorescein sodium < eosin < congo red < phenol red < thymol blue < safranine-T < methylene blue < rhodamine-B (94.2%). The efficiency of rhodamine-B for 3S aluminium in 0.1 M solutions of various amines in creases in the order: monoethanolamine (75.4%) < cyclohexylamine < n-butylamine < triethylamine < n-propylamine < diethylamine < trimethylamine < diethanolamine < ethylenediamine < triethanolamine < dimethylamine < ethylamine < methylamine (94.2%). The increase in corrosion potential of 3S aluminium in 0.1 M amine containing 0.1% rhodamine-B and the galvanostatic polarization data indicate that the inhibitor has preponderant action on local anodes.     

Effect of volatile inhibitors from natural and amended soils on germination of sclerotia of Macrophomina phaseolina

Studies on volatile soil fungistasis showed that sclerotia of Macrophomina phaseolina are not sensitive to volatiles liberated by natural soils with varying pH values. Soil amended with alfalfa hay (1%, w/w) liberated volatiles fungistatic to sclerotia only when the assay was performed 2 weeks or less after amendment. Chitin-amended soils liberated fungistatic volatiles from 1 to 3 weeks after amendment. Indirect evidence indicated that ammonia may be the active volatile in amended soil. It was concluded that fungistatic volatiles may not play an important role in the survival of sclerotia in nature.     

Aldehydes as corrosion inhibitors for aluminium-manganese alloys in potassium hydroxide

Some aliphatic and aromatic aldehydes have been studied as corrosion inhibitors for 3S aluminium (Al-Mn alloy) in KOH solutions. At constant alkali concentration the inhibitor efficiency increases with the concentration of the inhibitor, the order of efficiency in 0.1 M KOH + 1.0% inhibitor being: paraldehyde (13.3%) < formaldehyde ≦ propionaldehyde < crotonaldehyde < furfuraldehyde < vanillin < salicylaldehyde (74.8%); 0.5% benzaldehyde and 0.1% cinnamicaldehyde gave efficiencies of only 19.3% and 18.5%, respectively. The aldehydes appear to act by adsorption on the metal surface, preferably through the oxygen atom. The inhibitive efficiency of paraldehyde increases with the alkali concentration, the duration of immersion and the temperature; that of formaldehyde, cinnamic aldehyde, furfuraldehyde (and crotonaldehyde) increases with alkali concentration and time; that of salicylaldehyde and vanillin increases with time as well as with temperature, while the efficiency of propionaldehyde and benzaldehyde increases with alkali concentration. The activation energy for the corrosion process is generally higher in inhibited than in plain alkali in the case of formaldehyde, propionaldehyde, crotonaldehyde, benzaldehyde, cinnamicaldehyde and furfuraldehyde; with other inhibitors the E values are lower. Except vanillin and paraldehyde, all the inhibitors increase the corrosion potential of Al in 0.1 M KOH suggesting polarization of local anodes. The inhibitor efficiencies calculated from extrapolation of cathodic Tafel lines are in agreement with weight loss efficiencies.     

Gonadotropin secretion and hypothyroidism

Hypothyroidism is generally associated with hypogonadotropism. Occasionally, however, increased gonadotropin concentrations are encountered. The mechanisms, presumably hypothalamic, which determine the gonadotropin shift are unclear. A case report of hyperprolactinemic hypothyroidism with associated hypergonadotropism is presented. The previous literature is reviewed. It appears that hypothyroidism is generally associated with a decrease in the gonadogropin secretion. However, hypothyroidism with exxagerated hTSH secretin and hyperprolactinemia can be associated with increased gonadotropin secretion.     

Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalate

The general properties of fundamental antisymmetric A0, symmetric S0, and shear horizontal SH0 acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). The results obtained will be useful for a proper development of various physical, chemical, and biological sensors and devices for signal processing based on plate acoustic waves.