Three novel dendritic chitosan derivatives for inhibiting acid corrosion of petroleum pipelines

In the process of exploration and development of oil and gas fields, the acidic environment of oil reservoir, production and transport processes cause corrosion of pipelines and equipment, resulting in huge economic losses and production safety risks. Corrosion inhibitors were widely used in oil industry because of simple operation process and economical. In this study, three environmentally friendly corrosion inhibitors were synthesized based on the natural polysaccharide chitosan. Corrosion inhibition of three dendritic chitosan derivatives (We name them BH, CH and DH) on mild steel in 1 mol/L HCl solution with natural ventilation system was evaluated by weight loss experiment, electrochemical analysis and surface morphology characterization. The experimental results showed that when the three dendritic chitosan derivatives added in the corrosive medium were 500 mg L^(−1), the corrosion inhibition efficiencies were all more than 80%. Based on quantum chemical calculation, inhibition mechanisms of three dendritic chitosan derivatives were investigated according to molecular structures. The results showed that the benzene ring, Schiff base and N atom contained in the molecule were the active centers of electron exchange, which were more likely to form a film on the carbon steel surface, thereby slowing or inhibiting corrosion. The results also predicted the corrosion inhibition effect BH > DH > CH, which was consistent with the experimental conclusion.

Dissolutive wetting process and interfacial characteristic of molten Sn–17Bi–0.5Cu alloy on copper substrate

The reactive spreading processes of Sn–17Bi–0.5Cu melt alloy on Cu substrate were studied by sessile drop method in the temperature range of 523–673 K.Dynamic contact angles between the solder and Cu substrate at different times were recorded with high-resolution CCD digital video.The smallest contact angle was observed at623 and 673 K.Ultimate spreading radius does not increase monotonously with the temperature increasing.These can be attributed to the strong dissolution of Cu substrate into the liquid solder,which hinders the solder from spreading.Triple line area configuration of the Sn–17Bi–0.5Cu/Cu system was discussed by the description of the equilibrium state.The calculated results based on experiments of the tension balances along each of the three interfaces show good agreement with theoretical analysis.Intermetallic compounds at the Sn–17Bi–0.5Cu/Cu interface are identified as Cu6Sn5adjacent to the solder and Cu3Sn adjacent to the Cu substrate,respectively.These results are of practical interest for composite lead-free solders’preparations and joining of Sn–17Bi–0.5Cu to Cu substrate.

Marangoni Bifurcation Flow in a Microchannel T-Junction and Its Micropumping Effect: A Computational Study

We discuss a bifurcation phenomenon of Marangoni flow in a microchannel T-junction and its novel unidirectional pumping effect.The T-junction is formed by a main channel connected with a liquid reservoir and a side channel outlet to the atmosphere.A volatizing meniscus is formed in the side channel and Marangoni convections are generated due to the non-uniform evaporation on the meniscus.It is found for weak evaporations (Ma < 270) the Marangoni convections are symmetrical.However,for intense evaporations (Ma > 270),the initial inward symmetrical Marangoni convection becomes unstable and converted into one single vortex flow.Moreover,the single vortex induces a steady unidirectional flow in the main channel,acting like a pump.

Observation of Nucleate Boiling on a Fine Copper Wire with Superhydrophobic Micropatterns

Hydrophobic islands/patterns on a hydrophilic substrate could be employed to enhance boiling heat transfer,however the underlying mechanisms are far from clear.We perform boiling experiments on a copper wire coated with superhydrophobic micropatterns(contact angle>170°).The copper wire is as fine as 150μm in diameter,greatly facilitating the observation of the bubble dynamic details.With the heat flux increasing,four regimes are characterized based on the bubble behavior.The superhydrophobic micropatterns are found to play critical roles in bubble formation and distribution as well as the interactions.