AbstractCertain S‐containing organic compounds were synthesized and their extreme pressure (EP) properties assessed. The series of compounds studied were: S‐alkylisodithiobiurets, alkyl‐S‐alkyl xanthates, S‐alkylisothioamides, S‐benzylisothiocarbamides and 1‐formamidino‐2‐benzyliso‐3‐arylthiocarbamides. These additives were compared with a commercial additive. The tribological end effects were studied using a Scanning Electron Microscope. Some of the compounds tested were found to be effective EP additives.Wherever possible, a plausible explanation for the enhanced activity has been given, and we have attempted to correlate the effect of substituents on efficiency. Also, the effect of additives on balls of different compositions is discussed. The possibility of replacing the costly chromium steel alloy balls by less costly mild steel balls is suggested.Some of the additives developed are found to be effective on balls of certain compositions while they are a total failure on the chromium steel balls. The studies reveal that some additives are effective on mild steel balls as well as chromium alloy steel balls. They can be very good substitutes for commercial additives with bearing balls of standard composition.As chromium alloy steel balls are much costlier there is a need to replace expensive alloy steel balls with cheaper low carbon steel balls, for certain specific purposes. This can be achieved by using suitable indigenous additives that are found to be effective on low carbon steel balls.

Load carrying capacities of certain 1-formamidino-2-S-benzyliso-3-arylthiocarbamides were assessed using a four-ball extreme-pressure (ep) lubricant testing machine. All the compounds tested were found to be effective at high loads. 1-formamidino-2-S-benzyliso-3-phenylthiocarbamide was potentially useful at high loads; m-chlorophenyl- and p-tolyl derivatives were effective at low loads as well. For a comparative study a reference additive was used. Scanning electron microscopy was used to study the tribological properties.

The corrosion behaviour of some aluminium alloys (1060, 1100 and 3003) in acidic chloride solution (pH=1) have been studied in the presence of various concentrations of tungstate ions. The alloy most vulnerable to the effects of tungstate ions is 1100 followed by 1060 and 3003 alloys. After six hours of immersion the alloys exhibit 6 to 8 times higher corrosion rates compared to that in the blank solution containing only chloride ions. The experiments suggest that the tungstate ion stimulates the corrosion of aluminium by acting as a cathodic depolarizer. Morpholine effectively arrests the dissolution of the alloys in the blank electrolyte as well as in the presence of tungstate ions. Morpholine polarizes local cathodic sites to act as an inhibitor. Tungstate ions are not adsorbed on the surface in the presence of morpholine and a synergistic effect is obtained at higher concentrations of morpholine. A Langmuir adsorption isotherm has been used to explain the data.

AbstractDas Korrosionsverhalten der handelsüblichen A1‐Legierungen 1060, 1 100, 3003 und 5052 wird in Abhängigkeit von der HNO3‐Konzentration und der Temp. untersucht.

The corrosion inhibiting efficiencies of guanidine carbonate and some of its condensation products have been demonstrated for aluminium (1060) in 20% nitric acid at 25° and 35°C. The percentage inhibitive efficiencies (IE, %) have been found to increase with a rise in temperature and also with an increase in concentration of the inhibitors up to 500 ppm. All the condensation products exhibit greater inhibitive efficiency than the parent compound (guanidine carbonate). 1-p-Methoxyphenyl-3-formamidino-thiocarbamide was found to be the most effective inhibitor followed by 1-p-Methylphenyl-3-formamidino-thiocarbamide, 1-p-Chlorophenyl-3-formamidino-thiocarbamide, 1-m-Chlorophenyl-3-formamidino-thiocarbamide and guanidine carbonate. In each case the steady state potential attained a more negative value with increase in concentration of the additives. Potentiostatic (anodic and cathodic) polarisation studies revealed that the inhibitors are predominantly effective on local cathodes, although partially e...

The synthesis of certain S-benzylisothiocarbamides and the assessment of their extreme pressure (ep) properties are reported. These additives were compared with a commercial additive. The tribological end effects were studied using a scanning electron microscope. m-chlorophenyl and p-tolyl-S-benzylisothiocarbamides were found to be potentially effective. The mechanism of ep activity is discussed and a theory put forward to explain the ep additive-metal interaction.

Corrosion characteristics of some commercially pure aluminum alloys (1060, 1100, 3003, and 5052) in different concentrations of nitric acid have been studied at different temperatures. Alloy 3003 exhibits maximum corrosion in all the acid concentrations followed by 5052, 1100, and 1060 alloys. The corrosion rate of aluminum is found to increase and decrease with time in 20 and 70% acid solutions, respectively. In the concentration range of 20–50% of the acid, all the alloys exhibited slightly passivating tendency during the potentiostatic anodic polarization. The breakdown potential of the alloys varies inversely with temperature, whereas an invariable enobling in steady‐state corrosion potential with rise in temperature is noted. The current density required for initiation of passivation, i.e. is related to temperature by

Inhibition and polarization properties of urea, thiourea (TU), acetyl thiourea (AcTu), phenyl thiourea (PhTu), o-tolyl thiourea (o-tol Tu), m-tolyl thiourea (m-tol Tu), p-tolyl thiourea (p-tol Tu), 1:3-diphenyl thiourea (di-phTu), 1:3-di-o-tolyl thiourea (di-o tol Tu), 1:3-di-m-tolyl thiourea (di-m-tol Tu) and 1 : 3-di-p-tolyl thiourea (di-p-tol Tu) have been studied in relation to the corrosion of aluminium (1060) in 20% nitric acid. The polarization experiments were carried out using potentiostatic method. The inhibition efficiencies of the inhibitors were determined at 25°, 35° and 45°C and it has been observed that the percentage inhibition efficiencies of the inhibitors increase with increase in temperature. All the inhibitors except urea obey the Langmuir adsorption isotherm below the inhibitor concentration of 300 ppm, but in no case are slopes equal to unity observed. At and above the concentration of 300 ppm, the effectiveness of the compounds decreases, which is attributed to their action as cathodic depolarizers. The inhibitive performance of the compounds is discussed in the light of electronic effects in the thioureas. The potentiostatic anodic polarization curves in the presence of the inhibitors shift towards lower current density region as compared with the curve of the uninhibited solution, but there is no proper correlation between the inhibition efficiencies and the current densities required for the passivation of aluminium.

A study has been made on the inhibitive efficiency of some thioureas (urea, thiourea, phenylthiourea and naphthylthiourea), in the concentration range 0.0025 to 2%, in relation to dissolution of some aluminium alloys (1060, 1100, 3003 and 5052) in 20% nitric acid solution at temperatures of 25, 35 and 45° C. It was found that the structures of the thioureas affected the inhibitive efficiency but the mechanism of inhibition remained the same. The compounds exhibited maximum protection in the concentration range 0.025 to 0.03%. A gradual lowering in the efficiency of the compounds above the concentration of 0.03% has been observed. At the concentration of 1.5%, urea appears to be a corrosion accelerator and causes localized attack on the alloy surface; the other compounds still showed some degree of inhibition. The additives were most efficient towards 1060 alloy, followed by 1100, 3003 and 5052 alloys. The protecting power of all the compounds other than urea was found to improve with increase in temperature. All the compounds appeared to inhibit corrosion by adsorbing at cathodic sites. A distinctive hump (i.e. a current maximum) is observed in the steady-state potentiostatic anodic polarization curves of the alloys. This hump is found to be affected by the inhibitors. At higher concentrations, the compounds act as cathodic depolarizers, which is confirmed by measuring steady-state corrosion potentials and cathodic polarization diagrams.

Certain S-alkylisothioamides were synthesized and their load-carrying capacities assessed using a Seta Shell four-ball machine. S-benzylisothiobenzamide was found to be potentially attractive.

A number of aryl/alkyl-dithiocarbamates have been assessed as extreme pressure additives using a Seta-Shell four-ball lubricant testing machine. p-Tolyl dithiocarbamate and o-tolyl dithiocarbamate were found to be effective.

The inhibitive efficiencies of isatin, thiosemicarbazide and their condensation product, i.e. isatin-3-(3-thiosemicarbazone) are studied at different concentrations in relation to corrosion of aluminium alloys (1060,1100, 3003) in 20% nitric acid at 30, 40 and 50° C using the weight loss method. Polarization experiments have been performed at 0.05, 0.2 and 0.3% concentrations of the inhibitors at 30° C. It is found that isatin-3-(3-thiosemicarbazone) is a more effective inhibitor as compared to the parent compounds for the three alloys at all the experimental temperatures. The effectiveness of the inhibitors increases with increase in temperature from 30° C to 50° C. The inhibitors are found to retard the corrosion by predominantly acting on local cathodes although they are also partially effective on the anodes. The critical current density for the passivation of aluminium decreases almost in the same order as the inhibition efficiency of the inhibitors increases.

The inhibitive efficiencies of thiourea and some of its derivatives have been studied in relation to the corrosion of aluminium (Grade 1060) in nitric acid at 25°c, 35°c and 45°c. The efficiency in 20% HNO3 at 25°c decreases in the order: p-chlorophenyl thiourea > m-chlorophenyl thiourea ≥ o-chlorophenyl thiourea ≥ phenyl urea > 1:3 di-phenyl thiourea ≥ 1:3 di-p-chlorophenyl thiourea. ≥ 1:3 di-m-chlorophenyl thiourea > thiourea. The adsorption of the compounds is in agreement with Langmuir's adsorption isotherm equation up t a concentration of 250 ppm, at all the three temperatures studied. The percentage efficiencies of the inhibitors were found to increase with increase in temperature from 25° to 45°c. There is no relation between the relative efficiencies of the inhibitors and their critical current densities or primary passivation potentials. All the inhibitors were found to act predominantly on local cathodes although partially effective on the anodes.

AbstractDer N‐Arylthioharnstoff (I) wird mit p‐Chlorbenzylchlorid (II) am Schwefelatom zu (III) alkyliert und anschließend mit den Isothiocyanaten (IV) zu den Isodithiobiureten (V) umgesetzt.