The inhibition of BTA from erosion-corrosion of BFe30-1-1 in single and sand-containing artificial seawater have been investigated using rotating cylinger apparatus.The methods adopted in the experiments were weight loss and electrochemical measurements insluding linear polarization resistance and potentiodynamic scanning as well as electrochenical inpedance spectroscopy..The results showed that BTA could significantly retarede both the anodic and cathodic reactions of BFe30-1-1 in the media by geometric blocking effect.The adsorption of BTA on the alloy followed Langmiur isotherm.BTA showed better ingibition action in flowing seawater than in static seawater.however,the ingibiting action of BTA decreased then the fluid velocity of artificial seawater was even higher.Furthrmore,the ingibition efficiency of BTA in sand-containing artificial seawater decreased with increasing sand content probably due to the strong mechanical erosion action of sand against electrode surface.

The environmental fracture behavior of 304 stainless steel base metal and three weld metals with different alloy additions(A002,A132 and A302)under as-welded and postweld heat treatment (PWHT)conditions were quantitatively studied in 0.5mol/L NaCl+2.5mol/L H2SO4 solution at room temperature.The tests were carried out with a cantilever bending test machine and the da/dt～K1 curves were determined to evaluate the resistance to environmental fracture.The micrography,fractography and electrochemical tests for corrosion were performed for mechanism study. The results showed that K ISCC of the weld metals was 30～39MPa m1/2,increasing in order of A002,A302and A132,being 62%～79% of the base metal,and their da/dt reached to (5～7)×10-6mms-1,being 2.8～3.9 times of the base metal.As the PWHT temperature increased,the susceptibility to environmental fracture for the weld metals decreased.The environmental fracture behavior of 304 base metal was controlled by stress assisted active tunnels,showing transgranular(TG)fracture.However,the environmental fracture behavior of the weld metals were mainly controlled by pre-existing actuve tunnel mechanism.showing intergranular(IG)or IG+TGmode.Since the delta ferrite in the weld metals was an anodic phase to be preferentially corroded,forming pre-existent active tunnels,the resistance to environmental fracture decreased as the ferrite content increased and a continuous network formed.The environmental fracture behavior of 304 steel weld metals was mainly dependent on the ferrite content and morphology.Both the weld metal composition and PWHT would affect the resistance to environmental fracture through the change of microstructure.

The scale inhibition effect of four methylenephosphonic acids with structure(HO)2OPCH2{N[CH2PO(OH)2]CH2CH2}n N[CH2PO(OH)2]2 (n=0,1,2,3,4)was compared by dynamic and static test methods.A dynamic mechanism of scale retarding effect was proposed based on analysis and calculation of the experimental data.The experimental results of dynamic method was different from those of static method in two aspects.First, according to dynamic tests the scale inhibition effect of the methylenephosphonic acides was not monotonously enhanced with the increase of their concentration,it may be weakened after a certain dosage.Second,their scale inhibition effect varied in the order:ATMP(m=3)＜EDTMP(m=4)＜TETHMP(m=6)＜DETPMP(m=5) from the dynamic tests rather than ATMP(m=3)＜EDTMP(m=4)＜DETPMP(m=5)＜TETHMP(m=6) from the static tests,here m referred to the number of CH2PO(OH)2group in a methylenephosphonic acid molecule.It was also found that the scale inhibition effect of the inhibitors was mainly due to the retarding of CaCO3 crystal growth rather than the reducing of the amount of calcium ions in solution.

1-[(1'-imidazolly)-methy] benzotriazole(IMBTA) was synthesized by Mannich reaction.Its inhibition effects for copper corrosion in 3% NaCl solution was investigated by weight-loss measurement,electrochemical polarization curves and electrochemical impedance spectra.IMBTA(0.001mol/L)exhibited better protection compared with the mixture of 0.001mol/L benzotriazole (BTA)and 0.001mol/ L inidazole (IM)under the same experimental conditions.Polarization studies showed that IMBTS supressed both cathodic and anodic corrosion reactions.The synergistic effect of BTA moiety and IM moiety in IMBTA molecule was observed.The electron transfer from IM moiety to BTA moiety was conductive to the adsorption of BTA moiety on copper surface.This resulted in improvement of the protective ability of IMBTA for copper in 3% NaCl solution

EIS and other techniques were used to study the behavior of steel P110 in CO2-containing simulated oilfield brine at room temperature and pressure.It was found that the most important reason of H2CO3 being more corrosive than a xompletely dissociated acid resulted from an additional cathodic reaction:the direct reduction of H2CO3.The impedance spectra at both open circuit potential and anodic potential presented a typical character of three time constants:a capacitive semicircle was followed by an inductuve and a small capacitive demicircle at low frequencies.This and other obxervations suggested that the active dissloution of steel P110 at relatively lower pH in the simulated fluid took place by "pH-dependent mechanism".The cathodic reactions mainly included H+ reduction,direct H2CO3 reduction,HCO3 reduction and direct H2O reduction.The dominance of four reactions in cathodic current changed with pH of the media

In this paper,the biofilm of sulfate reducing bacteria(SRB)which plays an important role in corrosion of carbon steel under anaerobic condition has been studied.The postgate medium was used to culture Jianghan oilfield SBR.Electrochemical impedance spectroscopy(EIS)was used to analyse the electrode process of carbon steel with SBR biofilm.The advantage of EIS lies in its minor disturbance of surface effect of the biofilm.X-ray diffraction and gas chromatography and mass spectrometry(GC/MS)techniques were used to analyse the corrosion products and the metabolites of SRB.The results showed that the main metablites of SRB sampled from Jianghan oilfield were butanic and benzoic acid and the corrosion products contained FeS and Fe2P. The variation of activit of the SRB biofilm with SRB growth can be found from the EIS in SRB-inoculation media.The extracellular polymeric substance of biofilm stimulated the concentration of nutrition and corrosion products,so it could accelerate the corrosion process.

The aluminum matrix composite reinforced by SiC whisker have been extensively studied because of their excellent properties.But little was known about the stress corrosion cracking (SCC)behavior of SiCw/Al composite.In the present research,the effect of annealing treatment on the SCC behavior of SiCw /Al and SiC/2024 composites was investigated using Double-Cantilever-Beam(DCB)specimen in 3.5%NaCl solution.The results indicated that annealing treatment improved the SCC behavior of the two composites by residual stress and changing matrix microstructure.With the increase in annealing temperature,the SCC propagation rate of the two composites decreased and the K ISCC increased.The TEM observation showed that dislocation density in matrix of the composites decreased greatly after annealing treatment.As a result,the sensibility to SCC of the composites was improved.

An apparatus for erosion-corrosion test in liquid-particle two-phase flow with Laser-doppler-anemometry (LDA)system was constructed.It can be used to simulate the erosion-corrosion behavior under disturbed flow conditiions.The local hydrodynamic parameters of disturbed flow such as axial and tangential velocty and its turbulence as well as turbulent fluctuation can be measured by LDA system.The results of both hydrodynamic measurements and weight loss test of suden expansion flow model showed that the set-up works well and the data are comparable with literature

The corrosion performance of mild steel A3 in oilfield refilling water containing oil flooding reagent such as polymer HPAM and petroleum sulfonate (PS)has been investigated by immersion weight loss, potentiodynamic polarization and EIS.It was found that mild steel was under active dissolution in both HPAM and PS solutions.Inhibition efficiency of HPAM increased with the increade in its concentration.EIS presented a single capacitive loop,showing the characteristics of HPAM absorption.However,EIS in PS solution indicated two capacitive loops with lower dispersion coefficient.Moreover,when the PS concentration exceeded 0.06%(w/w).beyond its CMC(critical micelle concentration ) in aqueous solution,its inhibition efficiency decreased due to the desorption of PS from steel surface.

The effect of MnCl2 applied on surface of Ti47Al2Cr2Nb quaternary alloy on its isothermal oxidation behavior at 900℃ has been studied.The presence of MnCl2 reduced the oxidation rate of the alloy by a factor of 3,and changed the scale composition from a mixture of TiO2 and Al2O3 to basically pure Al2O3.The reason for the improvement of oxidation resistance of the alloy due to MnCl2 was discussed.At the beginning of oxidation titanium in the alloy reacted with Cl to form substable titanium chloride.which vaporized and left alloy surface.As a result,a layer of compact Al2O3 scale formed on the alloy asuface and prevented the outward diffudion of titanium.

The corrosion character of seamud and corrosion electrochemical behavior of carbon steel in seamud were studied by electrochemical impedance spectroscopy.The experimental results showed that the seamud was aggressive in corrosion activity,and that corrosion potential of carbon steel in seamud was -0.75V(SCE),corrosion rate controlled by oxygen diffusion was 2.3μA/cm2, and hydrogen-evolution potential was -0.87V(SCE).The results also indicated that the rust on carbon steel surface led to the inductance inpedance behavior at high frequency during electrochemical impedance measurement.