Copper Alloy Surfaces Research Articles

Application of sol–gel method for the conservation of copper alloys

In the present study, SiO2 coatings are presented as an alternative to the traditional ones, used in conservation of metals. The preparation of methyl–modified nanosilica coatings by the sol–gel technique to protect the external surface of copper alloys is discussed herein. The methyl–modified silica sols were obtained by mixing of 3% SiO2 sol solution with hexamethyldisilozane (HMDS). The surface of brass and bronze specimens was coated by dip-coating technique. The structural features of the coatings were evaluated by FTIR spectroscopy. The hydrophobicity of the surfaces was investigated by contact angle measurements. The surface morphology changes of bare and coated specimens prior and after photochemical ageing were evaluated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Potentiodynamic measurements were obtained in order to compare corrosion parameters of the coatings.

Research of Lubrication Model and Surface Quality in Cold-Rolling Copper Alloy Using O/W Emulsions

Abstract A theoretical model for cold-rolling copper alloy in mixed lubrication regime was developed based on the average volume flow model and asperity flattening model. The developed scheme was able to calculate oil concentration λ d at any point within work zone, lubricant pressure, contact area ratio and film thickness ratio with different oil viscosity, pass reduction and the initial oil concentration λ ds . According to the lubrication model, for getting good lubrication and cooling effect of emulsions in rolling process, the rolling oil viscosity was selected in the range from 40 mm 2 /s to 50 mm 2 /s, the pass reduction about 30% and the initial oil concentration λ ds of emulsion in the range from 0.02 to 0.05. For verifying the lubrication model, the last nonseizure load was tested by the four-ball tests to confirm oil viscosity and initial oil concentration, and the rolled copper alloy surface topographies were analyzed to confirm pass reduction. The results show that the calculation data agree well with the measured data from experiment. They provide technical references for selecting rolling process parameters and emulsions.

Antimicrobial copper alloy surfaces are effective against vegetative but not sporulated cells of gram-positive Bacillus subtilis.

This study explores the role of membrane phospholipid peroxidation in the copper alloy mediated contact killing of Bacillus subtilis, a spore-forming gram-positive bacterial species. We found that B. subtilis endospores exhibited significant resistance to copper alloy surface killing but vegetative cells were highly sensitive to copper surface exposure. Cell death and lipid peroxidation occurred in B. subtilis upon copper alloy surface exposure. In a sporulation-defective strain carrying a deletion of almost the entire SpoIIA operon, lipid peroxidation directly correlated with cell death. Moreover, killing and lipid peroxidation initiated immediately and at a constant rate upon exposure to the copper surface without the delay observed previously in E. coli. These findings support the hypothesis that membrane lipid peroxidation is the initiating event causing copper surface induced cell death of B. subtilis vegetative cells. The findings suggest that the observed differences in the kinetics of copper-induced killing compared to E. coli result from differences in cell envelop structure. As demonstrated in E. coli, DNA degradation was shown to be a secondary effect of copper exposure in a B. subtilis sporulation-defective strain.

From Laboratory Research to a Clinical Trial: Copper Alloy Surfaces Kill Bacteria and Reduce Hospital-Acquired Infections.

Objective:This is a translational science article that discusses copper alloys as antimicrobial environmental surfaces. Bacteria die when they come in contact with copper alloys in laboratory tests. Components made of copper alloys were also found to be efficacious in a clinical trial.Background:There are indications that bacteria found on frequently touched environmental surfaces play a role in infection transmission.Methods:In laboratory testing, copper alloy samples were inoculated with bacteria. In clinical trials, the amount of live bacteria on the surfaces of hospital components made of copper alloys, as well as those made from standard materials, was measured. Finally, infection rates were tracked in the hospital rooms with the copper components and compared to those found in the rooms containing the standard components.Results:Greater than a 99.9% reduction in live bacteria was realized in laboratory tests. In the clinical trials, an 83% reduction in bacteria was seen on the copper alloy components, when compared to the surfaces made from standard materials in the control rooms. Finally, the infection rates were found to be reduced by 58% in patient rooms with components made of copper, when compared to patients' rooms with components made of standard materials.Conclusions:Bacteria die on copper alloy surfaces in both the laboratory and the hospital rooms. Infection rates were lowered in those hospital rooms containing copper components. Thus, based on the presented information, the placement of copper alloy components, in the built environment, may have the potential to reduce not only hospital-acquired infections but also patient treatment costs.

Study on Anti-Corrosion Property of Nickel-Based Coatings on Copper Surface in Supersonic Particles Deposition

In this study, the anti-corrosion properties of nickel-based coatings on the surface of copper alloy were investigated, and damages caused by corrosion on the copper surface were resolved. Researchers prepared nickel-based coatings by supersonic particles deposition, and tested the anti-corrosion properties of brass substrate and nickel-based coating by electrochemical technology and neutral salt spray. The results show that, the corrosion current of coating decreased 35 times than that of matrix. The successive and pyknotic oxide film on the surface of coating prevented reaction of corrosion further. When it reached 500 hours, the corrosion rate closed to 0. Nickel-based coatings prepared by supersonic particles deposition contribute to the increase of corrosion resistance significantly, which verifies that it is feasible to prepare outstanding corrosion resisting nickel-based coating by supersonic particles deposition.

Destruction of the Capsid and Genome of GII.4 Human Norovirus Occurs during Exposure to Metal Alloys Containing Copper.

Human norovirus (HuNoV) represents a significant public health burden worldwide and can be environmentally transmitted. Copper surfaces have been shown to inactivate the cultivable surrogate murine norovirus, but no such data exist for HuNoV. The purpose of this study was to characterize the destruction of GII.4 HuNoV and virus-like particles (VLPs) during exposure to copper alloy surfaces. Fecal suspensions positive for a GII.4 HuNoV outbreak strain or GII.4 VLPs were exposed to copper alloys or stainless steel for 0 to 240 min and recovered by elution. HuNoV genome integrity was assessed by reverse transcription-quantitative PCR (RT-qPCR) (without RNase treatment), and capsid integrity was assessed by RT-qPCR (with RNase treatment), transmission electron microscopy (TEM), SDS-PAGE/Western blot analysis, and a histo-blood group antigen (HBGA) binding assay. Exposure of fecal suspensions to pure copper for 60 min reduced the GII.4 HuNoV RNA copy number by ∼3 log10 units when analyzed by RT-qPCR without RNase treatment and by 4 log10 units when a prior RNase treatment was used. The rate of reduction of the HuNoV RNA copy number was approximately proportional to the percentage of copper in each alloy. Exposure of GII.4 HuNoV VLPs to pure-copper surfaces resulted in noticeable aggregation and destruction within 240 min, an 80% reduction in the VP1 major capsid protein band intensity in 15 min, and a near-complete loss of HBGA receptor binding within 8 min. In all experiments, HuNoV remained stable on stainless steel. These results suggest that copper surfaces destroy HuNoV and may be useful in preventing environmental transmission of the virus in at-risk settings.

Inactivation of murine norovirus on a range of copper alloy surfaces is accompanied by loss of capsid integrity.

Norovirus is one of the most common causes of acute viral gastroenteritis. The virus is spread via the fecal-oral route, most commonly from infected food and water, but several outbreaks have originated from contamination of surfaces with infectious virus. In this study, a close surrogate of human norovirus causing gastrointestinal disease in mice, murine norovirus type 1 (MNV-1), retained infectivity for more than 2 weeks following contact with a range of surface materials, including Teflon (polytetrafluoroethylene [PTFE]), polyvinyl chloride (PVC), ceramic tiles, glass, silicone rubber, and stainless steel. Persistence was slightly prolonged on ceramic surfaces. A previous study in our laboratory observed that dry copper and copper alloy surfaces rapidly inactivated MNV-1 and destroyed the viral genome. In this new study, we have observed that a relatively small change in the percentage of copper, between 70 and 80% in copper nickels and 60 and 70% in brasses, had a significant influence on the ability of the alloy to inactivate norovirus. Nickel alone did not affect virus, but zinc did have some antiviral effect, which was synergistic with copper and resulted in an increased efficacy of brasses with lower percentages of copper. Electron microscopy of purified MNV-1 that had been exposed to copper and stainless steel surfaces suggested that a massive breakdown of the viral capsid had occurred on copper. In addition, MNV-1 that had been exposed to copper and treated with RNase demonstrated a reduction in viral gene copy number. This suggests that capsid integrity is compromised upon contact with copper, allowing copper ion access to the viral genome.

Comparative Analysis of Triazine Self-Assembled Nanofilm with/without Fluorine Substituent on Copper Alloy Surface

Comparative Analysis of Triazine Self-Assembled Nanofilm with/without Fluorine Substituent on Copper Alloy Surface

Corrosion Behavior of HSn70-1 Copper Alloy in SRB Containing Medium in Atatic Magnetic Field

The corrosion behavior of HSn70-1copper alloy in sulfate-reducing bacteria (SRB) con- taining medium in the absence and presence of a static magnetic field (SMF) respectively was in- vestigated by means of weight loss method, electrochemical measurement and surface analysis method. The results showed that the corrosion weight loss and the corrosion current density of the alloy was higher in the inoculated SRB medium in the absence of SMF rather than those in the pres- ence of SMF. Thus the presence of a SMF can suppress effectively the corrosion of copper alloy. The results of SEM/EDS, XRD and XPS analysis showed that in the inoculated SRB medium a compact and uniform film formed on the surface of copper alloy in the presence of SMF, the corro- sion products were cuprous sulfide; however in the absence of SMF the formed corrosion product on the alloy was loose and consisted of cupric sulfide. In fact the compact corrosion scale of cu- prous sulfide could effectively suppress the SRB induced corrosion of copper alloy.

Correction: Inactivation of Norovirus on Dry Copper Alloy Surfaces

Correction: Inactivation of Norovirus on Dry Copper Alloy Surfaces

DFT Prediction of Oxygen Reduction Reaction on Palladium–Copper Alloy Surfaces

The high cost of proton exchange membrane fuel cells (PEMFCs) comes largely from the use of platinum-containing electrocatalysts. Despite significant progress made the past decade on reducing the platinum catalyst loading in the PEMFC electrodes, further substantial cost reductions require the replacement of platinum with less expensive nonplatinum electrocatalytic materials. In this study, PdCu alloys have computationally been investigated as possible non-Pt catalysts for oxygen reduction reaction (ORR) in PEMFCs. We used density functional theory (DFT) calculations to determine the structural preference and ORR activity as a function of the composition and structure. Five PdCu alloy surface structures, B2, L12, L10, L11-nonlayered, and L11-layered, were considered, and the layered L11 surface structure was found to exhibit significantly improved ORR kinetics compared to that of pure Pd.

Dual function of benzotriazole as copper alloy corrosion inhibitor and hydrochloric acid flow improver

The corrosion of copper-nickel alloy in hydrochloric acid has been investigated at different temperatures, benzotrizole concentrations and corrosive solution velocities. Weight loss technique has been used to evaluate the corrosion rate data. Results obtained have proved that benzotrizole has a dual effect by reducing both metal corrosion and flow losses. Maximum inhibition efficiency was 91.5%, while maximum drag reduction was 52.4%. Several mathematical equations are suggested successfully to represent the data with high correlation coefficients. Molecular dynamic simulations have been also performed to investigate the adsorption behavior of the inhibitor on the copper alloy surface. One of the novelties of the given work is the analogy between the corrosion process and fluid flow, as well as the investigation of the dual effect of benzotriazole on the corrosion process and the flow losses.

Research on Fretting Performance of Silver Conducting Adhesive

Fretting is one of the main reasons for electric contact failure. Metal contact pairs have long been used, generally with the structure of copper alloy base, Ni interlayer and surface noble metal (such as gold) plating. The influences of plating material and plating thickness on fretting property have been researched deeply, meanwhile, new materials have been tried. In this paper, a new conductive material, silver conducting adhesive is used as the surface coating of contact pair, and a series of tests have been done to study the performance of fretting wear by compare with the coupons without silver conducting adhesive. The results show that the use of silver conductive adhesive improves the fretting property of electrical contacts, especially with small normal force.

Inactivation of Norovirus on Dry Copper Alloy Surfaces

Noroviruses (family Caliciviridae) are the primary cause of viral gastroenteritis worldwide. The virus is highly infectious and touching contaminated surfaces can contribute to infection spread. Although the virus was identified over 40 years ago the lack of methods to assess infectivity has hampered the study of the human pathogen. Recently the murine virus, MNV-1, has successfully been used as a close surrogate. Copper alloys have previously been shown to be effective antimicrobial surfaces against a range of bacteria and fungi. We now report rapid inactivation of murine norovirus on alloys, containing over 60% copper, at room temperature but no reduction of infectivity on stainless steel dry surfaces in simulated wet fomite and dry touch contamination. The rate of inactivation was initially very rapid and proportional to copper content of alloy tested. Viral inactivation was not as rapid on brass as previously observed for bacteria but copper-nickel alloy was very effective. The use of chelators and quenchers of reactive oxygen species (ROS) determined that Cu(II) and especially Cu(I) ions are still the primary effectors of toxicity but quenching superoxide and hydroxyl radicals did not confer protection. This suggests Fenton generation of ROS is not important for the inactivation mechanism. One of the targets of copper toxicity was the viral genome and a reduced copy number of the gene for a viral encoded protein, VPg (viral-protein-genome-linked), which is essential for infectivity, was observed following contact with copper and brass dry surfaces. The use of antimicrobial surfaces containing copper in high risk closed environments such as cruise ships and care facilities could help to reduce the spread of this highly infectious and costly pathogen.

Can Copper Lower Infection Rates

Contamination of the hospital environment contributes to the acquisition of multidrug-resistant organisms and the development of hospital-acquired infections (HAIs) — a realization that has led to increasing emphasis on disinfection. But might changing surface materials also be beneficial? Two new studies suggest that the use of copper-alloy surfaces could be effective in decreasing HAIs. (One of the authors, who participated in both studies, is employed by the Copper Development Association.) Schmidt and colleagues compared the bacterial burden (BB) on copper-covered and …

Copper Surfaces Reduce the Rate of Healthcare-Acquired Infections in the Intensive Care Unit

OBJECTIVE. Healthcare-acquired infections (HAIs) cause substantial patient morbidity and mortality. Items in the environment harbor microorganisms that may contribute to HAIs. Reduction in surface bioburden may be an effective strategy to reduce HAIs. The inherent biocidal properties of copper surfaces offer a theoretical advantage to conventional cleaning, as the effect is continuous rather than episodic. We sought to determine whether placement of copper alloy-surfaced objects in an intensive care unit (ICU) reduced the risk of HAI. DESIGN. Intention-to-treat randomized control trial between July 12, 2010, and June 14, 2011. SETTINg. The ICUs of 3 hospitals. PATIENTS. Patients presenting for admission to the ICU. METHODS. Patients were randomly placed in available rooms with or without copper alloy surfaces, and the rates of incident HAI and/or colonization with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE) in each type of room were compared. RESULTS. The rate of HAI and/or MRSA or VRE colonization in ICU rooms with copper alloy surfaces was significantly lower than that in standard ICU rooms (0.071 vs 0.123; P = .020). For HAI only, the rate was reduced from 0.081 to 0.034 (P = .013). CONCLUSIONs. Patients cared for in ICU rooms with copper alloy surfaces had a significantly lower rate of incident HAI and/or colonization with MRSA or VRE than did patients treated in standard rooms. Additional studies are needed to determine the clinical effect of copper alloy surfaces in additional patient populations and settings.

Horizontal Transfer of Antibiotic Resistance Genes on Abiotic Touch Surfaces: Implications for Public Health

ABSTRACTHorizontal gene transfer (HGT) is largely responsible for increasing the incidence of antibiotic-resistant infections worldwide. While studies have focused on HGT in vivo, this work investigates whether the ability of pathogens to persist in the environment, particularly on touch surfaces, may also play an important role. Escherichia coli, virulent clone ST131, and Klebsiella pneumoniae harboring extended-spectrum-β-lactamase (ESBL) blaCTX-M-15 and metallo-β-lactamase blaNDM-1, respectively, exhibited prolonged survival on stainless steel, with approximately 104 viable cells remaining from an inoculum of 107 CFU per cm2 after 1 month at 21°C. HGT of bla to an antibiotic-sensitive but azide-resistant recipient E. coli strain occurred on stainless steel dry touch surfaces and in suspension but not on dry copper. The conjugation frequency was approximately 10 to 50 times greater and occurred immediately, and resulting transconjugants were more stable with ESBL E. coli as the donor cell than with K. pneumoniae, but blaNDM-1 transfer increased with time. Transconjugants also exhibited the same resistance profile as the donor, suggesting multiple gene transfer. Rapid death, inhibition of respiration, and destruction of genomic and plasmid DNA of both pathogens occurred on copper alloys accompanied by a reduction in bla copy number. Naked E. coli DNA degraded on copper at 21°C and 37°C but slowly at 4°C, suggesting a direct role for the metal. Persistence of viable pathogenic bacteria on touch surfaces may not only increase the risk of infection transmission but may also contribute to the spread of antibiotic resistance by HGT. The use of copper alloys as antimicrobial touch surfaces may help reduce infection and HGT.

Sustained Reduction of Microbial Burden on Common Hospital Surfaces through Introduction of Copper

The contribution of environmental surface contamination with pathogenic organisms to the development of health care-associated infections (HAI) has not been well defined. The microbial burden (MB) associated with commonly touched surfaces in intensive care units (ICUs) was determined by sampling six objects in 16 rooms in ICUs in three hospitals over 43 months. At month 23, copper-alloy surfaces, with inherent antimicrobial properties, were installed onto six monitored objects in 8 of 16 rooms, and the effect that this application had on the intrinsic MB present on the six objects was assessed. Census continued in rooms with and without copper for an additional 21 months. In concert with routine infection control practices, the average MB found for the six objects assessed in the clinical environment during the preintervention phase was 28 times higher (6,985 CFU/100 cm(2); n = 3,977 objects sampled) than levels proposed as benign immediately after terminal cleaning (<250 CFU/100 cm(2)). During the intervention phase, the MB was found to be significantly lower for both the control and copper-surfaced objects. Copper was found to cause a significant (83%) reduction in the average MB found on the objects (465 CFU/100 cm(2); n = 2714 objects) compared to the controls (2,674 CFU/100 cm(2); n = 2,831 objects [P < 0.0001]). The introduction of copper surfaces to objects formerly covered with plastic, wood, stainless steel, and other materials found in the patient care environment significantly reduced the overall MB on a continuous basis, thereby providing a potentially safer environment for hospital patients, health care workers (HCWs), and visitors.

Membrane Lipid Peroxidation in Copper Alloy-Mediated Contact Killing of Escherichia coli

Copper alloy surfaces are passive antimicrobial sanitizing agents that kill bacteria, fungi, and some viruses. Studies of the mechanism of contact killing in Escherichia coli implicate the membrane as the target, yet the specific component and underlying biochemistry remain unknown. This study explores the hypothesis that nonenzymatic peroxidation of membrane phospholipids is responsible for copper alloy-mediated surface killing. Lipid peroxidation was monitored with the thiobarbituric acid-reactive substances (TBARS) assay. Survival, TBARS levels, and DNA degradation were followed in cells exposed to copper alloy surfaces containing 60 to 99.90% copper or in medium containing CuSO(4). In all cases, TBARS levels increased with copper exposure levels. Cells exposed to the highest copper content alloys, C11000 and C24000, exhibited novel characteristics. TBARS increased immediately at a very rapid rate but peaked at about 30 min. This peak was associated with the period of most rapid killing, loss in membrane integrity, and DNA degradation. DNA degradation is not the primary cause of copper-mediated surface killing. Cells exposed to the 60% copper alloy for 60 min had fully intact genomic DNA but no viable cells. In a fabR mutant strain with increased levels of unsaturated fatty acids, sensitivity to copper alloy surface-mediated killing increased, TBARS levels peaked earlier, and genomic DNA degradation occurred sooner than in the isogenic parental strain. Taken together, these results suggest that copper alloy surface-mediated killing of E. coli is triggered by nonenzymatic oxidative damage of membrane phospholipids that ultimately results in the loss of membrane integrity and cell death.

Mechanism of copper surface toxicity in Escherichia coli O157:H7 and Salmonella involves immediate membrane depolarization followed by slower rate of DNA destruction which differs from that observed for Gram‐positive bacteria

We have reported previously that copper I and II ionic species, and superoxide but not Fenton reaction generated hydroxyl radicals, are important in the killing mechanism of pathogenic enterococci on copper surfaces. In this new work we determined if the mechanism was the same in non-pathogenic ancestral (K12) and laboratory (DH5α) strains, and a pathogenic strain (O157), of Escherichia coli. The pathogenic strain exhibited prolonged survival on stainless steel surfaces compared with the other E. coli strains but all died within 10 min on copper surfaces using a 'dry' inoculum protocol (with approximately 10(7) cfu cm(-2) ) to mimic dry touch contamination. We observed immediate cytoplasmic membrane depolarization, not seen with enterococci or methicillin resistant Staphylococcus aureus, and loss of outer membrane integrity, inhibition of respiration and in situ generation of reactive oxygen species on copper and copper alloy surfaces that did not occur on stainless steel. Chelation of copper (I) and (II) ionic species still had the most significant impact on bacterial survival but protection by d-mannitol suggests hydroxyl radicals are involved in the killing mechanism. We also observed a much slower rate of DNA destruction on copper surfaces compared with previous results for enterococci. This may be due to protection of the nucleic acid by the periplasm and the extensive cell aggregation that we observed on copper surfaces. Similar results were obtained for Salmonella species but partial quenching by d-mannitol suggests radicals other than hydroxyl may be involved. The results indicate that copper biocidal surfaces are effective for Gram-positive and Gram-negative bacteria but bacterial morphology affects the mechanism of toxicity. These surfaces could not only help to prevent infection spread but also prevent horizontal gene transmission which is responsible for the evolution of virulent toxin producing and antibiotic resistant bacteria.