Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test（SSRT） in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking（SCC） behavior of 7003 aluminum alloy（AA7003） in acid and alkaline chloride solutions under various applied potentials（Ea）. The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution（AD） at open-circuit potential（OCP） and is highly susceptible to hydrogen embrittlement（HE） at high negative Ea in the solutions with p H levels of 4 and 11. The susceptibility increases with negative shift in the potential when Ea is less than-1000 m V vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when Ea is equal to-1000 m V vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

INTERPHASE STRESS CORROSION CRACKING OF ALLOY Ti－24Al－11Nb IN METHANOL SOLUTION

For alloy Ti-24Al-11Nb,stress corrosion cracking(SCC) in methanol solution and hydrogen induced cracking(HIC) during dynamic charging at room temperature have been studied.Experiment has shown that the normalised threshold stress intensities of SCC failure for various microstructures are KISCC/KC =0.53 0.69 and the threshold value for SCC arresting KISCC/ KIC=0.61-0.79.The threshold values of HIC during dynamic charging are close to that of SCC,but da/dt or fracture time of HIC is one to three orders of magnitude smaller or longer than that of SCC,respectively.The.fracture surface for HIC is also different from that for SCC.For the Ti-24Al-Nb alloy-methanol systein,a kind of inierphase SCC has been found For the microstructures resulting from furnace cooling,SCC initiated and propagated preferentially along theα2/βinterphase boundaries,displaying the microstructure on the fracture surface of SCC.However,there is no interphase SCC for the microstructure resulting from air cooling.

Analysis of cracks origin behaviors during sulfide stress corrosion (SSC) in HSLA steel at different temperatures by electrochemical noise

The sulfide stress corrosion(SSC)behaviors of the high strength low alloy steel at the different temperatures were investigated by the microstructural observation and electrochemical noise(EN)analysis.With the corrosion temperature increasing from 20 to 40℃,SSC ruptured time is prolonged.The increase in corrosion temperature results in the decrease of the saturation solubility of H_(2)S in the solution and thus increases pH value of solution.The increase in corrosion temperature decreases the size of the holes and cracks in the corrosion product film on the surface of the sample,which is due to the formation of the dense FeS corrosion product film.The current kurtosis results indicate that the time for the first occurrence of crack initiation is postponed by the increase in the corrosion temperature.The standard deviation of current noise signals,current kurtosis,power spectral density and energy distribution plot results shows a great consistency,which suggests that EN analysis method can reflect SSC behaviors in real time.

Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel

Hydrogen induced cracking（HIC） behaviors of a high strength pipeline steel with three different microstructures, granular bainite ＆ lath bainite（GB ＋ LB）, granular bainite ＆ acicular ferrite（GB ＋ AF）, and quasi-polygonal ferrite（QF）, were studied by using corrosion experiment based on standard NACE TM0284. The HIC experiment was conducted in hydrogen sulfide（H_2S）-saturated solution. The experimental results show that the steel with GB ＋ AF and QF microstructure present excellent corrosion resistance to HIC, whereas the phases of bainite lath and martensite/austenite in LB ＋ GB microstructure are responsible for poor corrosion resistance. Compared with ferrite phase, the bainite microstructure exhibits higher strength and crack susceptibility of HIC. The AF ＋ GB microstructure is believed to have the best combination of mechanical properties and resistance to HIC among the designed steels.

In-situ physical/chemical cross-linked hydrogel electrolyte achieving ultra-stable zinc anode-electrolyte interface towards dendrite-free zinc ion battery

Hydrogen evolution reaction(HER),zinc corrosion,and dendrites growth on zinc metal anode are the major issues limiting the practical applications of zinc-ion batteries.Herein,an in-situ physical/chemical cross-linked hydrogel electrolyte(carrageenan/polyacrylamide/ZnSO_(4),denoted as CPZ)has been developed to stabilize the zinc anode-electrolyte interface,which can eliminate side reactions and prevent dendrites growth.The in-situ CPZ hydrogel electrolyte improves the reversibility of zinc anode due to eliminating side reactions caused by active water molecules.Furthermore,the electrostatic interaction between the SO_(4)^(-)groups in CPZ and Zn^(2+)can encourage the preferential deposition of zinc atoms on(002)crystal plane,which achieve dendrite-free and homogeneous zinc deposition.The in-situ hydrogel electrolyte offers a streamlined approach to battery manufacturing by allowing for direct integration into the battery.Subsequently,the Zn//Zn half battery with CPZ hydrogel electrolyte can enable an ultra-long cycle over 5500 h at a current density of 0.5 mA cm^(-2),and the Zn//Cu half battery reach an average coulombic efficiency of 99.37%.The Zn//V_(2)O_5-GO full battery with CPZ hydrogel electrolyte demonstrates94.5%of capacity retention after 2100 cycles.This study is expected to open new thought for the development of commercial hydrogel electrolytes for low-cost and long-life zinc-ion batteries.

SCC investigation of low alloy ultra-high strength steel 30CrMnSiNi2A in 3.5wt% NaCl solution by slow strain rate technique

To evaluate stress corrosion cracking（SCC） mechanism of low alloy ultra-high strength steel 30CrMnSiNi2 A in environment containing NaCl, SCC behavior of the steel in 3.5wt% NaCl solution is investigated by slow strain rate technique（SSRT） with various strain rates and applied potentials, surface analysis technique, and electrochemical measurements. SCC susceptibility of the steel increases rapidly with strain rate decreasing from 1 · 10 5s 1to 5 · 10 7s 1, and becomes stable when strain rate is lower than 5 · 10 7s 1. SCC propagation of the steel in the solution at open circuit potential（OCP） needs sufficient hydrogen which is supplied at a certain strain rate.Fracture surface at OCP has similar characteristics with that at cathodic polarization 1000 mVSCE, which presents characteristic fractography of hydrogen induced cracking（HIC）.All of these indicate that SCC behavior of the steel in the solution at OCP is mainly controlled by HIC rather than anodic dissolution（AD）.