Chunguang Yang

Accelerated corrosion of 2205 duplex stainless steel caused by marine aerobic Pseudomonas aeruginosa biofilm.

Microbiologically influenced corrosion (MIC) of 2205 duplex stainless steel (DSS) in the presence of Pseudomonas aeruginosa was investigated through electrochemical and surface analyses. The electrochemical results showed that P. aeruginosa significantly reduced the corrosion resistance of 2205 DSS. Confocal laser scanning microscopy (CLSM) images showed that the depths of the largest pits on 2205 DSS with and without P. aeruginosa were 14.0 and 4.9μm, respectively, indicating that the pitting corrosion was accelerated by P. aeruginosa. X-ray photoelectron spectroscopy (XPS) results revealed that CrO3 and CrN formed on the 2205 DSS surface in the presence of P. aeruginosa.

Laboratory investigation of the microbiologically influenced corrosion (MIC) resistance of a novel Cu-bearing 2205 duplex stainless steel in the presence of an aerobic marine Pseudomonas aeruginosa biofilm

The microbiologically influenced corrosion (MIC) resistance of a novel Cu-bearing 2205 duplex stainless steel (2205 Cu-DSS) against an aerobic marine Pseudomonas aeruginosa biofilm was investigated. The electrochemical test results showed that Rp increased and icorr decreased sharply after long-term immersion in the inoculation medium, suggesting that 2205 Cu-DSS possessed excellent MIC resistance to the P. aeruginosa biofilm. Fluorescence microscope images showed that 2205 Cu-DSS possessed a strong antibacterial ability, and its antibacterial efficiency after one and seven days was 7.75% and 96.92%, respectively. The pit morphology comparison after 14 days between 2205 DSS and 2205 Cu-DSS demonstrated that the latter showed a considerably reduced maximum MIC pit depth compared with the former (1.44 μm vs 9.50 μm). The experimental results suggest that inhibition of the biofilm was caused by the copper ions released from the 2205 Cu-DSS, leading to its effective mitigation of MIC by P. aeruginosa.

Study on behaviour and mechanism of Cu2+ ion release from Cu bearing antibacterial stainless steel

Abstract Cu bearing stainless steels (Cu SS) possess antibacterial ability due to the release of Cu2+ ions. However, the release mechanism of Cu2+ ions from the steel is still unclear. Therefore, the passive film on the surface of Cu SS, the reason of Cu2+ ions release and chemical reactions during Cu2+ ions release were studied by means of X-ray photoelectron spectroscopy analysis and electrochemical measurements. According to the results, the release mechanism of Cu2+ ions release from the Cu SS can be proposed as following: Cu rich phases in the steel promote the segregation of surrounding C and Cr to form Cr23C6, which affects the integrity and stability of the Cr2O3 passive film surrounding themselves. Thus, the Cu rich phases are easy to be attacked as weak points in the corrosive media, which led to serial chemical reactions occurring while promoting the releases of Cu2+ ions and playing the antibacterial role.

A novel coping metal material CoCrCu alloy fabricated by selective laser melting with antimicrobial and antibiofilm properties

OBJECTIVE The aim of this study was to fabricate a novel coping metal CoCrCu alloy using a selective laser melting (SLM) technique with antimicrobial and antibiofilm activities and to investigate its microstructure, mechanical properties, corrosion resistance and biocompatibility. METHODS Novel CoCrCu alloy was fabricated using SLM from a mixture of commercial CoCr based alloy and elemental Cu powders. SLM CoCr without Cu served as control. Antibacterial activity was analyzed using standard antimicrobial tests, and antibiofilm properties were investigated using confocal laser scanning microscope. Cu distribution and microstructure were determined using scanning electron microscope, optical microscopy and X-ray diffraction. Corrosion resistance was evaluated by potential dynamic polarization and biocompatibility measured using an MTT assay. RESULTS SLM CoCrCu alloys were found to be bactericidal and able to inhibit biofilm formation. Other factors such as microstructure, mechanical properties, corrosion resistance and biocompatibility were similar to those of SLM CoCr alloys. SIGNIFICANCE The addition of appropriate amounts of Cu not only maintains normal beneficial properties of CoCr based alloys, but also provides SLM CoCrCu alloys with excellent antibacterial and antibiofilm capabilities. This material has the potential to be used as a coping metal for dental applications.

Preliminary assessment of metal-porcelain bonding strength of CoCrW alloy after 3wt.% Cu addition.

In this work, a novel Cu-bearing CoCrW alloy fabricated by selective laser melting for dental application has been studied. For its successful application, the bonding strength of metal-porcelain is essential to be systematically investigated. Therefore, the aim of this study was to evaluate the metal-porcelain bonding strength of CoCrWCu alloy by three-point bending test, meanwhile the Ni-free CoCrW alloy was used as control. The oxygen content was investigated by an elemental analyzer; X-ray photoelectron spectroscopy (XPS) was used to analyze the surface chemical composition of CoCrW based alloy after preoxidation treatment; the fracture mode was investigated by X-ray energy spectrum analysis (EDS) and scanning electron microscope (SEM). Result from the oxygen content analysis showed that the content of oxygen dramatically increased after the Cu addition. And the XPS suggested that Co-oxidation, Cr2O3, CrO2, WO3, Cu2O and CuO existed on the preoxidated surface of the CoCrWCu alloy; the three-point bending test showed that the bonding strength of the CoCrWCu alloy was 43.32 MPa, which was lower than that of the CoCrW group of 47.65 MPa. However, the average metal-porcelain bonding strength is significantly higher than the minimum value in the ISO 9693 standard. Results from the SEM images and EDS indicated that the fracture mode of CoCrWCu-porcelain was mixed between cohesive and adhesive. Based on the results obtained in this study, it can be indicated that the Cu-bearing CoCrW alloy fabricated by the selective laser melting is a promising candidate for use in dental application.

Effect of copper addition on mechanical properties, corrosion resistance and antibacterial property of 316L stainless steel

The effects of addition of different Cu content (0, 2.5 and 3.5wt%) on mechanical properties, corrosion resistance and antibacterial performance of 316L austenitic stainless steel (SS) after solution and aging treatment were investigated by mechanical test, transmission electron microscope (TEM), X-ray diffraction (XRD), electrochemical corrosion, X-ray photoelectron spectroscopy (XPS) and antibacterial test. The results showed that the Cu addition and heat treatment had no obvious influence on the microstructure with complete austenite features. The yield strength (YS) after solution treatment was almost similar, whereas the aging treatment obviously increased the YS due to formation of tiny Cu-rich precipitates. The pitting and protective potential of the solution treated Cu-bearing 316L SS in 0.9wt% NaCl solution increased with increasing Cu content, while gradually declined after aging, owing to the high density Cu-rich precipitation. The antibacterial test proved that higher Cu content and aging were two compulsory processes to exert good antibacterial performance. The XPS results further indicated that aging enhanced the Cu enrichment in passive film, which could effectively stimulate the Cu ions release from the surface of passive film.

Effect of Cu content on antibacterial activity of 17-4 PH stainless steel

Abstract The 17-4 PH stainless steels with four different copper (Cu) contents were fabricated, and their antibacterial performances were studied by means of antibacterial test, TEM observation, Vickers hardness measurement and electrochemical test. The results showed that the Cu seriously influenced the antibacterial performance of 17-4 PH stainless steel. The higher the Cu content in the steel, the better the antibacterial activity and the higher the micro-hardness of the 17-4 PH stainless steel. The Cu content in the 17-4 PH stainless steel should be above 4·5 wt-% to exhibit better antibacterial activity. The electrochemical test showed that the Cu content would also affect the Cu ions release behaviour of the 17-4 PH stainless steel, which eventually influence the antibacterial activity.

Effect of aging on antibacterial performance of Cu-bearing martensitic stainless steel

Abstract A preliminary study was made on the antibacterial performance and hardness of a type 420 Cu-bearing martensitic stainless steel (420-Cu) by antibacterial test, Vickers hardness measurement and TEM observation. The results showed that with increase of the aging temperature, the antibacterial performance of the 420-Cu steel was improved, but the hardness declined quickly. With prolonging the aging time at 500°C, both antibacterial rate and hardness increased. Combining the results of antibacterial test and hardness measurement, an optimal aging treatment for the 420-Cu steel was proposed.

Optimized antibacterial treatment for the Cu-bearing 420 stainless steel

ABSTRACT Cu-bearing antibacterial martensitic stainless steel (MSS) has a broad application prospect in cutting field, which needs a combination of good antibacterial property and high hardness. In this work, 420Cu stainless steel (SS) with high Cu addition and different austenitizing temperatures were investigated to address the above issue. The results of plate count measurement and biofilm observation indicated that 420Cu SS austenitized at lower temperature shows better antibacterial performance. The Rockwell hardness was up to 52.7 HRC and corrosion resistance evaluated by electrochemical polarization was also acceptable. Scanning electron microscope (SEM) observation further revealed that the treated 420Cu SS possessed of the martensitic microstructure with more undissolved carbides and Cu-rich precipitations, which led to the higher hardness. Mott-Schottky and inductively coupled plasma-mass spectrometry (ICP-MS) tests implied that above precipitations decrease the compactness of passive film and then promote the release of Cu ions, which ensured the 420Cu SS good antibacterial property.