Sang Xiong

Tribological Performance and Wear Mechanism of Compound Containing S, P, and B as EP/AW Additives in Copper Foil Oil

ABSTRACT Research and development on the high biodegradability of additives is indispensable for environmentally friendly lubricants, which is one of the key factors to advance lubricant technology toward “greener” chemistry. The tribological performance of fatty alcohol polyoxyethylene phosphate acid ester (EK), boron-containing amide (BT), dialkyl dithiophosphate ester (DDE), and a mixture of these (compound) as extreme pressure (EP)/antiwear (AW) additives in hydrogenated base oil (GH) were investigated using a four-ball testing machine. The elemental composition and chemical characteristics of the AW films generated on the surfaces of the steel balls were studied using X-ray photoelectron spectroscopy (XPS), and their AW mechanisms are hereby proposed. Thermal degradation tests were conducted to identify their thermal stabilities using thermogravimetry and differential scanning calorimetry. The results show that these additives can greatly improve the EP/AW properties of GH. XPS analyses of the worn surfaces indicate that decomposed borate esters and organic sulfide or nitrides were adsorbed on the worn surface, and the P and S elements of the compound reacted with the metal and existed in the form of phosphates and sulfates, both of which contributed to the formation of a boundary lubricating film. Moreover, these additives provide the lubricants with excellent oxidation resistance and thermal stability.

QSPR Models for the Prediction of Friction Coefficient and Maximum Non-Seizure Load of Lubricants

A quantitative structure–property relationship (QSPR) model was used to study the friction coefficient and maximum non-seizure load of fatty acids, alcohols, and esters as extreme pressure and antiwear additives in lubricants on the surface of steel using several physicochemical descriptors. The tribological properties of these compounds on the steel surface were studied using a four-ball tribo-tester. Molecular refractivity and several structural descriptors were adopted in the development of the QSPR using a genetic function approximation (GFA) statistical analysis method. The results show that quantum descriptors are a better choice for predicting the friction coefficient and maximum non-seizure load of lubricants. Hydrogen bond donor, dipole, polarizability, molecular refractivity, and surface area are the most sensitive among the major contributing descriptors.

QSAR Study on Imidazole Derivatives as Corrosion Inhibitors by Genetic Function Approximation Method

Quantitative structure and activity relationship (QSAR) method is becoming more desirable for predicting of corrosion inhibition properties. The inhibition efficiency of organic compounds is dependent on many basic molecular descriptors, including structural descriptors, thermodynamic descriptors, information content descriptors, topological descriptors as Wiener index, Zagreb index and molecular connectivity indices. A genetic function approximation approach was used to run the regression analysis and establish correlations between different types of descriptors and measured corrosion inhibition efficiency for imidazole derivatives. A QSAR equation was developed and used to predict the corrosion inhibition efficiency for 18 imidazole derivatives. The prediction of corrosion efficiencies of these compounds nicely matched the experimental measurements.

Adsorption behavior of tautomeric forms of 2-aminino-5-mercato-1,3,4 – thiadizole as corrosion inhibitor on copper surface

Purpose The purpose of this study is to evaluate the effect of the four tautomeric forms of 2-amino-5-mercatpo-1,3,4-thiadizole (AMT) absorbed on copper surface by the polar or non-polar groups. Polar group of AMT is mostly electronegative with larger N and S atoms as central atoms. 5-amino-1,3,4-thiadiazole-2(3H)-thion (AMT-c) has the highest adsorption energy and is easy to react with copper. The interaction between AMT-c and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement. Design/methodology/approach Adsorption behavior of AMT as corrosion inhibitor on copper surface in oil field was studied by weight loss measurement, and the corrosion inhibition mechanism was analyzed. Reactive sites and distributions of tautomeric forms of AMT as inhibitor on Cu(100) crystal plane were calculated by density functional theory. Findings All atoms of AMT are in the same plane, and AMT is an aromatic ring structure by large p-chain adsorbed on the metal surface by a plane configuration. AMT-c has the highest adsorption energy and also the most stable isomerized product. The determinate locations of AMT on the Cu(100) surface are the bridge and the hollow sites using molecular dynamics. Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Inhibition efficiency is increased with the increase in the concentration of the inhibitor. The maximum efficiency of 92 per cent is obtained for 50 ppm AMT concentration at 373 K, which is attributed to the presence of extensively delocalized electrons of the phenyl rings, planarity and the presence of lone pair of electrons on N and S atoms, which favored a greater adsorption of inhibitors on copper surface. Originality/value Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Adsorption of AMT as corrosion inhibitor on copper surface obeys Langmuir isotherm. The interaction between AMT and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement.