Inhibitive efficiency

High inhibitive efficiency relative to thermal destruction of n-alkanes is displayed by hydrides and amides of alkali metals [33-35]. 

Fiber glass provides effective inhibition of polyethylene thermal destruction up to 400°C. The inhibitive efficiency increases with increased content of sodium oxide from 0.7-16% (Table 5). 

According to the ionization potential and electron-transfer work, alkali metals form the following series Li > Na > K, and their hydroxides are arranged in the sequence KOH > NaOH > LiOH as to their inhibitive efficiency relative to thermal destruction of polyolefins. And the efficiency of alkali metals can be represented by the sequence Na > K > Li. This seems to be due... 

The inhibitive efficiency of alkali metal hydroxides increases with increased branching of polyethylene. This is confirmed by more pronounced effect of these hydroxides diminishing the yield of propane and propylene than in case of ethane and ethylene. The decreased yield of propane and propylene is also conditioned by more efficient inhibition of the macroradical isomerization stage by alkali metal hydroxides. Upon thermal destruction of polyethylene with the use of inhibitors the... 

The inhibitive efficiency of boric acid polyesters differs greatly. The highest efficiency is exhibited by polyesters of boric acid, aromatic diols and triols. This derives from the fact that in this case the radicals are accepted not only by boron, but also by the aromatic nucleus. Among the aromatic polyesters, most efficient is ester of boric acid and pyrocatechin due to the Frank-Rabinovich cage effect. The efficiency of inhibi-... 

Polypyrocatechin borate has a higher inhibitive efficiency relative to the reactions of the radical R2 than to that of the radical Ri, since the latter exerts a more severe decrease in the yield of propane and propylene than in the yield of ethane and ethylene, and favors an insignificant growth of polyethylene nonsaturation in the pro-... 

It is in this area that most work has been carried out, particularly in relation to corrosion resistance in sulphuric acid solutionsBourelier etal. and Raicheff etal. investigated the inhibitive effect of chloride ions on corrosion in sulphuric acid. The inhibition efficiency was found to depend on the alloy composition, alloy surface and chloride concentration. The more aggressive the environment, the greater the inhibition efficiency. Yagupol skaya etal studied the effect of iodine additions to sulphuric acid on the corrosion resistance of Ni and Ni-Fe alloys. Again there was an inhibitive effect caused by the halide ion. 

The information on inhibitor adsorption, derived from direct measurements and from inhibitive efficiency measurements, considered in conjunction with general knowledge of adsorption from solution indicates that inhibitor adsorption on metals is influenced by the following main factors. 

In the case of ions, the repulsive interaction can be altered to an attractive interaction if an ion of opposite charge is simultaneously adsorbed. In a solution containing inhibitive anions and cations the adsorption of both ions may be enhanced and the inhibitive efficiency greatly increased compared to solutions of the individual ions. Thus, synergistic inhibitive effects occur in such mixtures of anionic and cationic inhibitors . These synergistic effects are particularly well defined in solutions containing halide ions, I. Br , Cl", with other inhibitors such as quaternary ammonium cations , alkyl benzene pyridinium cations , and various types of amines . It seems likely that co-ordinate-bond interactions also play some part in these synergistic effects, particularly in the interaction of the halide ions with the metal surfaces and with some amines . 

Reaction of adsorbed inhibitors In some cases, the adsorbed corrosion inhibitor may react, usually by electro-chemical reduction, to form a product which may also be inhibitive. Inhibition due to the added substance has been termed primary inhibition and that due to the reaction product secondary inhibition " . In such cases, the inhibitive efficiency may increase or decrease with time according to whether the secondary inhibition is more or less effective than the primary inhibition. Some examples of inhibitors which react to give secondary inhibition are the following. Sulphoxides can be reduced to sulphides, which are more efficient inhibitorsQuaternary phosphonium and arsonium compounds can be reduced to the corresponding phosphine or arsine compounds, with little change in inhibitive efficiency . Acetylene compounds can undergo reduction followed by polymerisation to form a multimolecular protective film . Thioureas can be reduced to produce HS ions, which may act as stimulators of... 

The inhibitive efficiency of anions tends to increase with size in a homologous series , due probably to the increasing tendency to adsorption, and decreasing solubility of the ferric-anion complex. 

Same dangers of peroxidation and decomposition exist for the compounds formed. However, this peroxidation is inhibited efficiently by N-phenyl-1-naphthyiamine. 

The results on the cellular protection against N()2 can be interpreted as the N()2 reacting with the three antioxidants to produce their radicals, with ascorbic acid reacting least efficiently, probably due to the lower reduction potential of its radical. Moreover, Arroyo et al. (1992) reported that NO - and N02 -induced mutations in Salmonella typhimurium TA1535 were inhibited efficiently by P-CAR and tocopherols, but not at all by ascorbic acid. 

Electrochemical impedance spectroscopy was used to determine the effect of isomers of 2,5-bis( -pyridyl)-l,3,4-thiadiazole 36 (n 2 or 3) on the corrosion of mild steel in perchloric acid solution <2002MI197>. The inhibition efficiency was structure dependent and the 3-pyridyl gave better inhibition than the 2-pyridyl. X-ray photoelectron spectroscopy helped establish the 3-pyridyl thiadiazoles mode of action toward corrosion. Adsorption of the 3-pyridyl on the mild steel surface in 1M HCIO4 follows the Langmuir adsorption isotherm model and the surface analysis showed corrosion inhibition by the 3-pyridyl derivative is due to the formation of chemisorbed film on the steel surface. 

The primary selection of candidates was based on the inhibition efficiency. It was chosen to use two different experimental assays for testing the efficiency of the candidate inhibitors ... 

IF] measures the inhibition efficiency given by the inhibition constants AT/ from reaction III. 

Contradictory opinions have been referred to in the literature particularly on the nature of the iron-tarmate and its interaction with the rusted steel due to the diversity of the material used in different studies. Studies have included the use of tannic acid [7-10], gallic acid [11], oak tannin [12, 13], pine tannin [14] and mimosa tannin [15]. In order to establish the correlation between the ferric-taimate formation and the low inhibition efficiency observed at high pH from the electrochemical studies, phase transformations of pre-rusted steels in the presence of tannins were evaluated. In this work the quantum chemical calculations are conducted to analyse the relationship between the molecular stracture and properties of ferric-taimate complex and its inhibitory mechanism. 

Figtire 7.12 is the polarization curves of pyrite electrode in xanthate solution with different concentration for dipping for 48 hours. Electrochemistry parameters determined by the computer PARcal are listed in Table 7.2. Inhibiting efficiency can be calculated by Eq. (7-7), Rp- is the polarization resistance after adding collector, Rp is the polarization resistance without collector. It can be seen from Fig. 7.12 and Table 7.2 diat, with the increase of xanthate concentration, corrosive potential and corrosive current of the pyrite electrode decrease gradually while polarization resistance increases, indicating the formation of surface oxidation products. 

The inhibition efficiency of the triarylmethanes decreases as the oxygen partial pressure is increased because of a decrease in the steady-state concentration of the triarylmethyl radicals. 

As illustrated in Scheme 6.1, once the covalent intermediate is formed, the complex can either follow a normal catalytic cycle or go through a suicide event leading to the irreversible labeling that is necessary for selection. The suicide inhibition efficiency depends on the ratio k /k. This ratio depends on the nature of the suicide substrate and of the enzyme. Therefore, a large excess of suicide substrate as compared to the displayed enzyme is recommended for selection experiments. 

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