Microbiologically influenced corrosion resistance enhancement of coppercontaining high entropy alloy Fe_(x)Cu_(1−x)CoNiCrMn against Pseudomonas aeruginosa

To enhance the microbiologically influenced corrosion(MIC)resistance of FeCoNiCrMn high entropy alloy(HEAs),a series of Fe_(x)Cu_((1−x))CoNiCrMn(x=1,0.75,0.5,and 0.25)HEAs were prepared.Microstructural characteristics,corrosion behavior(morphology observation and electrochemical properties),and antimicrobial performance of Fe_(x)Cu_((1−x))CoNiCrMn HEAs were evaluated in a medium inoculated with typical corrosive microorganism Pseudomonas aeruginosa.The aim was to identify copper-containing FeCoNiCrMn HEAs that balance corrosion resistance and antimicrobial properties.Results revealed that all Fe_(x)Cu_((1−x))CoNiCrMn(x=1,0.75,0.5,and 0.25)HEAs exhibited an FCC(face centered cubic)phase,with significant grain refinement observed in Fe_(0.75)Cu_(0.25)CoNiCrMn HEA.Electrochemical tests indicated that Fe_(0.75)Cu_(0.25)CoNiCrMn HEA demonstrated lower corrosion current density(i_(corr))and pitting potential(E_(pit))compared to other Fe_(x)Cu_((1−x))CoNiCrMn HEAs in P.aeruginosa-inoculated medium,exhibiting superior resistance to MIC.Anti-microbial tests showed that after 14 d of immersion,Fe_(0.75)Cu_(0.25)CoNiCrMn achieved an antibacterial rate of 89.5%,effectively inhibiting the adhesion and biofilm formation of P.aeruginosa,thereby achieving resistance to MIC.

Functionalized carbon dots for corrosion protection:Recent advances and future perspectives

Metal corrosion causes significant economic losses,safety issues,and environmental pollution.Hence,its prevention is of immense research interest.Carbon dots(CDs)are a new class of zero-dimensional carbon nanomaterials,which have been considered for corrosion protection applications in recent years due to their corrosion inhibition effect,fluorescence,low toxicity,facile chemical modification,and cost-effectiveness.This study provides a comprehensive overview of the synthesis,physical and chemical properties,and anticorrosion mechanisms of functionalized CDs.First,the corrosion inhibition performance of different types of CDs is introduced,followed by discussion on their application in the development of smart protective coatings with self-healing and/or self-reporting properties.The effective barrier formed by CDs in the coatings can inhibit the spread of local damage and achieve self-healing behavior.In addition,diverse functional groups on CDs can interact with Fe^(3+)and H^(+)ions generated during the corrosion process;this interaction changes their fluorescence,thereby demonstrating self-reporting behavior.Moreover,challenges and prospects for the development of CD-based corrosion protection systems are also presented.

A comparative study of machine learning in predicting the mechanical properties of the deposited AA6061 alloys via additive friction stir deposition

Additive friction stir deposition(AFSD)provides strong flexibility and better performance in component design,which is controlled by the process parameters.It is an essential and difficult task to tune those parameters.The recent exploration of machine learning(ML)exhibits great potential to obtain a suitable balance between productivity and set parameters.In this study,ML techniques,including support vector machine(SVM),random forest(RF)and artificial neural network(ANN),are applied to predict the mechanical properties of the AFSD-based AA6061 deposition.Expect for the stable parameters(temperature,force and torque)in situ monitored by the self-developed process-aware kit during the AFSD process and the other factors(rotation speed,traverse speed,feed rate and layer thickness)are also set as input variables.The output variables are microhardness and ultimate tensile strength(UTS).Prediction results show that the ANN model performs the best prediction accuracy with the highest R2(0.9998)and the lowest mean absolute error(MAE,0.0050)and root mean square error(RMSE,0.0063).Furthermore,analysis suggests that the feed rate(24.8%/24.1%)and layer thickness(25.6%/26.6%)indicate a higher contribution that affects the mechanical properties.

Microbiologically Influenced Corrosion Behavior of Fe_(40)(CoCrMnNi)_(60) and Fe_(60)(CoCrMnNi)_(40) Medium Entropy Alloys in the Presence of Pseudomonas Aeruginosa

In this work,the microbiologically influenced corrosion(MIC)of Fe_(40)(CoCrMnNi)_(60) and Fe_(60)(CoCrMnNi)_(40) medium entropy alloys(MEAs)induced by Pseudomonas aeruginosa(P.aeruginosa)was investigated.Corrosion behaviors during 14 days of immersion in sterile and P.aeruginosa-inoculated culture media are presented.Under sterile conditions,both MEAs exhibited good corrosion resistance against the culture medium solution.In the presence of P.aeruginosa,the pitting corrosion of MEAs was promoted.The results of inductively coupled plasma‒mass spectrometry(ICP‒MS)and potentiodynamic polarization tests showed that the presence of P.aeruginosa promoted the selective dissolution of passive film and accelerated the corrosion of MEAs.The results of X-ray photoelectron spectroscopy(XPS)and Mott-Schottky measurements further demonstrated the degradation effect of P.aeruginosa on the passive film.Compared with Fe_(60)(CoCrMnNi)_(40),Fe_(40)(CoCrMnNi)_(60) manifested better resistance to the MIC caused by P.aeruginosa,which may be attributed to more Cr oxides and fewer Fe oxides of the passive film.

Microbiologically influenced corrosion of 304 stainless steel by halophilic archaea Natronorubrum tibetense

The corrosion behavior of 304 stainless steel(SS)in the presence of aerobic halophilic archaea Natronorubrum tibetense was investigated.After 14 days of immersion,no obvious pitting pit was observed on the SS surface in the sterile medium.By contrast,the SS exhibited serious pitting corrosion with the largest pit depth of 5.0μm in the inoculated medium after 14 days.The results of electrochemical tests showed that the barrier property of the passive film decreased faster in the inoculated medium.The X-ray photoelectron spectroscopy results indicated that the detrimental Fe2+and Cr6+increased in the passive film under the influence of archaea N.tibetense,which resulted in the accelerated deterioration of passive film and promoted the pitting corrosion.Combined with the energy starvation tests,the microbiologically influenced corrosion mechanism of 304 SS caused by halophilic archaea N.tibetense was discussed finally.

Mechanically durable antibacterial nanocoatings based on zwitterionic copolymers containing dopamine segments

Developing an effective and durable antibacterial surface is important for surgical tools and biomedical implants.In this work,a zwitterionic copolymer containing catechol groups as biomimetic anchoring segments was coated onto 316 L stainless steel via drop-casting.Energy-dispersive X-ray spectroscopy(EDS)and water contact angle(WCA)measurements indicated that the coatings made of the copolymers containing zwitterionic and dopamine segments at the molar ratios of 8:2 and 6:4 exhibited stronger stability and mechanical durability than the one at 9:1 after inducing tape-peeling and ultrasonication damage.The mechanically durable nanocoatings exhibited excellent antibacterial performance against Staphylococcus aureus and Escherichia coli in a period of 3 days.The nanocoatings with zwitterionic and dopamine segments at the molar ratio of 8:2 were further evaluated and demonstrated durable antibacterial performance after tape-peeling and ultrasonication treatments.

Microbiologically Influenced Corrosion of Q235 Carbon Steel by Aerobic Thermoacidophilic Archaeon Metallosphaera cuprina

The effect of thermoacidophilic archaeon Metallosphaera cuprina(M.cuprina)on the corrosion of Q235 carbon steel in its culture medium was investigated in this work.In the sterile culture medium,the carbon steels showed uniform corrosion morphologies and almost no corrosion products covered the sample surface during 14 days of immersion test.In the presence of M.cuprina,some corrosion pits appeared on the surface of carbon steels in the immersion test,exhibiting typical localized corrosion morphologies.Moreover,the sample surfaces were covered by a large number of insoluble precipitates during the immersion.After 14 days,the thickness of precipitates reached approximately 50μm.The results of weight loss test and electrochemical test demonstrated that the carbon steels in the M.cuprina-inoculated culture medium had higher corrosion rate than that in the sterile culture medium.The oxygen concentration cell caused by M.cuprina biofilms resulted in localized corrosion behavior,and the ferrous oxidation ability of M.cuprina accelerated the anodic dissolution of carbon steels,thus promoting the corrosion process of carbon steels.

Long-term deterioration of lubricant-infused nanoporous anodic aluminium oxide surface immersed in NaCl solution

This study investigated the deterioration of a lubricant-infused anodic aluminium oxide surface in a 1M NaCl solution for~200 days.Direct observation by cryo-SEM and quantitative analyses by UV spectroscopy and EIS revealed that the long-term deterioration of the lubricant-infused surface was divided into two stages:the surface-adhered lubricant layer gradually dissolved at a constant rate until the substrate was exposed;afterwards the lubricant infused in the nanochannels began to diffuse and was depleted after~200 days.The EIS results also revealed that the defects reduced the corrosion resistance of the lubricant-infused surface considerably.