Metal Substrata Research Articles

Probing the correlation between corrosion resistance and biofouling of thermally sprayed metallic substrata in the field

The correlation between inherent corrosion resistance and biofouling was investigated for five different metallic coatings. Steel panels thermally spray-coated with either aluminium, Monel, bronze or different aluminium alloys were tested in controlled salt mist conditions and electrochemical corrosion tests and subsequently employed at sea. The biofouling of the panels was monitored at different depths (5, 10 and 15 m) at periods ranging from 5 to 12 months. The main macrofouling organisms were quantified and analysed using permutational multivariate analysis. The results indicate a significant difference in fouling pressure between depths and the geographic sites used. No statistically significant link between high corrosion resistance and lower biofouling pressure was observed, indicating that the main marine macrofoulers settled equally well on corrosion resistant and corrosion prone metallic surfaces. This work sheds light on biofouling of thermally sprayed metallic substrata and it characterizes and compares biofouling assemblages from different biogeographical regions in Europe.

Endowing antifouling properties on metal substrata by creating an artificial barrier layer based on scalable metal oxide nanostructures

Here, by creating different types of artificial barrier layer against bacterial attachment, anti-biofouling properties were endowed on three metallic surfaces – aluminum, stainless steel and titanium. To each metallic surface, a tailored chemical oxidation process was applied to grow scalable oxide structures with an additional appropriate coating, resulting in three different types of anti-biofouling barrier, a thin water film, an air layer and an oil layer. Fluorescence images of the attached bacteria showed that the water layer improved the anti-biofouling performance up to 8–12 h and the air layer up to 12–24 h, comparable with the lifetime of the air layer. In comparison, the oil layer exhibited the best anti-biofouling performance by suppressing the fouled area by < 10% up to 72 h regardless of the substratum type. The present work provides simple, low-cost, scalable strategies to enhance the anti-biofouling performance of industrially important metallic surfaces.

Electrodeposition of aluminium from hydrophobic perfluoro-3-oxa-4,5 dichloro-pentan-sulphonate based ionic liquids

Aluminium electrodeposition from ionic liquids (ILs) prepared using a novel structure composed by perfluoro-3-oxa-4,5 dichloro-pentan-sulphonate [CF2ClCFClOCF2SO3−] and different cations is presented. The novel anion was designed by Solvay Specialty Polymers with the purpose to confer to the ionic liquids strong hydrophobic properties that facilitate the aluminium deposition in ambient conditions. Three cations, imidazolium, pyridinium and guanidinium are used to prepare the corresponding three liquids. In water, the resulting liquids prepared with imidazolium and pyridinium show very low miscibility and the liquid prepared with guanidinium is insoluble. Their electrochemical windows are dependent of both the cations and the substrate nature and are sufficiently wide to allow aluminium deposition. Even so, it was evidenced that the reduction of the new structure is not especially difficult. The AlCl3 was selected as useful source of Al(III) electroactive species to obtain coherent deposits. Using aluminium hydroxide, the coalescence of the aluminium deposits was not achieved.The viability of aluminium electrodeposition was, at first, tested on vitreous carbon, demonstrating it follows through a nucleation and growth process. As the practical interest carries to the use of metallic substrata, nickel was selected to analyse deposition process. The deposits prepared at constant current showed a better appearance, less stressed and smoother than the ones prepared at constant potential. The effect of temperature and concentration was studied in solutions prepared with tetramethyl guanidinium-perfluoro-3-oxa-4,5 dichloro-pentan-sulphonate, taking advantage of its immiscibility in water. Deposits prepared from the lower concentrations tested (AlCl3:IL 0.95:1 molar ratio) were continuous, fine grained and stress-free, provided that they were obtained at moderate applied current. From higher Al(III) concentration solutions it was only possible to allow stress-free deposits by applying low currents.

Electrochemical and surface analytical techniques applied to microbiologically influenced corrosion investigation

AbstractSuitable application of techniques for detection and monitoring of microbiologically influenced corrosion (MIC) is crucial for understanding the mechanisms of the interactions and for selecting inhibition and control approaches. This paper presents a review of the application of electrochemical and surface analytical techniques in studying the MIC process of metals and their alloys. Conventional electrochemical techniques, such as corrosion potential (Ecorr), redox potential, dual-cell technique, polarization curves, electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) analysis, and microelectrode techniques, are discussed, with examples of their use in various MIC studies. Electrochemical quartz crystal microbalance, which is newly used in MIC study, is also discussed. Microscopic techniques [scanning electron microscopy (SEM), environmental SEM (ESEM), atomic force microscopy (AFM), confocal laser microscopy (CLM), confocal laser scanning microscopy (CLSM), confocal Raman microscopy] and spectroscopic analytical methods [Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS)] are also highlighted. This review highlights the heterogeneous characteristics of microbial consortia and use of special techniques to study their probable effects on the metal substrata. The aim of this review is to motivate using a combination of new procedures for research and practical measurement and calculation of the impact of MIC and biofilms on metals and their alloys.

PANI-PMMA as cathodic electrode material and its application in cathodic polarization antifouling

Cathodic voltage applied to metal substrata has been proven to exhibit useful antifouling properties due to the generation of H2O2, where the metal substratum is used as a cathode in the process. However, most metals immersed in a marine environment are protected by insulating (anticorrosive) coatings, restricting the cathodic polarization that can be applied to the metal. In this work, polyaniline-polymethyl methacrylate was found to have good stability and low background current density, as measured by linear sweep voltammetry (LSV), chronoamperometry (CA) and cyclic voltammetry (CV), suggesting potential for use of PANI-PMMA as a cathode material. The antifouling effects of the PANI-PMMA coating on 24-h-old Escherichia coli bacteria (E. coli) were measured under different cathodic potentials and different polarization times; the outstanding antifouling effect was verified by fluorescence microscopy.

Stability of a Therapeutic Layer of Immobilized Recombinant Human Tropoelastin on a Plasma-Activated Coated Surface

To modify blood-contacting stainless surfaces by covalently coating them with a serum-protease resistant form of tropoelastin (TE). To demonstrate that the modified TE retains an exposed, cell-adhesive C-terminus that persists in the presence of blood plasma proteases. Recombinant human TE and a point mutant variant (R515A) of TE were labeled with (125)Iodine and immobilized on plasma-activated stainless steel (PAC) surfaces. Covalent attachment was confirmed using rigorous detergent washing. As kallikrein and thrombin dominate the serum degradation of tropoelastin, supraphysiological levels of these proteases were incubated with covalently bound TE and R515A, then assayed for protein levels by radioactivity detection. Persistence of the C-terminus was assessed by ELISA. TE was significantly retained covalently on PAC surfaces at 88 ± 5% and 71 ± 5% after treatment with kallikrein and thrombin, respectively. Retention of R515A was 100 ± 1.3% and 87 ± 2.3% after treatment with kallikrein and thrombin, respectively, representing significant improvements over TE. The functionally important C-terminus was cleaved in wild-type TE but retained by R515A. Protein persists in the presence of human kallikrein and thrombin when covalently immobilized on metal substrata. R515A displays enhanced protease resistance and retains the C-terminus presenting a protein interface that is viable for blood-contacting applications.

Bioaktive Werkstoffe

The bioactive materials should be divided into osteoinductive and osteostimulative materials according to their effect in bone regeneration. Already this statement requires a definition of the words used, in order to assure a real discussion. By means of the recommendations for definitions this paper is a basis for those discussions. In order to classify the bioactive materials into types of materials the potential effect onto the bone regeneration process should be considered. On the other hand the synthetic or biological origin, and the physical or biochemical structure are of great significance. Beside the classification made by the above called criteria the types of materials with their advantages and disadvantages are described. In the following discussion some problems are described like the mechanical and chemical instability, the coating of metallic substrata, the sterilization and the possibilities for the analytic characterization of hydroxylapatite.

Growth, characterization and biocompatibility of bone-like calcium phosphate layers biomimetically deposited on metallic substrata

Much research has been devoted to the coating of orthopedic and dental implants with porous ceramics, such as hydroxyapatite to increase hard tissue integration in vivo. Chemical immersion in simulated body fluids and supersaturated calcium-phosphate solutions (SCPS) have been shown to elicit apatite coatings on the order of 10–100 μm of thickness, which are very homogenous and would be more favorable to biological interaction than plasma-sprayed coatings. This study focuses on the growth, characterization and biocompatibility of bone-like apatite layers on metallic biomaterials produced through diminished time duration chemical immersion. The method presented here includes a pre-calcification step, in which samples were immersed in a boiling Ca(OH) 2 solution to initiate and increase favorable ion exchange prior to immersion. Subsequent immersion in SCPS produced homogenous coatings of calcium phosphate with a thickness of 20–30 μm, 100% coverage and crystal sizes of 1–2 μm in 3 days. Coated samples were favored biologically over non-coated samples by osteoblast cells as indicated by alkaline phosphatase activity. This study suggests that an industrially viable method of chemical immersion in a SCPS, coupled with simple pre-treatments can produce calcium phosphate coatings that favor positive biological interactions, conducive to osseointegration.

Calcium phosphate deposition from simulated milk ultrafiltrate on different stainless steel-based surfaces

Abstract In order to reduce the fouling caused by milk during heat treatment, it is important to know more about the precipitation process of calcium phosphate, the main mineral component of milk deposits. This work was mainly focused on the relationship between calcium phosphate fouling behaviour and the surface properties of the materials used as metallic substrata. The foulant solution used in this work was an aqueous solution that simulates the mineral composition of milk and the deposition of calcium phosphate was studied on several stainless steel-based surfaces with different surface energy properties, obtained by ion implantation (SiF 3 + and MoS 2 ), coating by plasma chemical vapor deposition (SiO x ) or autocatalytic coating (Ni-P-PTFE). The experiments were performed in a batch system, using a rotating disk apparatus. The calcium phosphate deposits formed were characterized according to the rate of formation, thickness and resistance to removal under increasing shear stresses. Based on the data presented in this work, it could be concluded that fouling caused by calcium phosphate is affected by the surface energy properties of the metal substrata since different surfaces develop different deposit structures which have, consequently, different resistance to removal.

Adsorption of flavobacterium breve and pseudomonas fluorescens p17 on different metals: Electrochemical polarization effect

The electrochemical polarization effect on early adsorption of Flavobacterium breve and Pseudomonas fluorescens P17 to platinum, titanium, stainless steel, copper, aluminum alloy and mild steel was studied. A well‐defined peak characterized the bacterial adsorption dependence on externally applied potential. Maximal adsorption occurred in the potential range of ‐0.5 to 0.5 V (SCE) for all tested metals. A shift of applied potential towards both a positive and a negative direction from the maximal adsorption potential (Emax,ad) was accompanied by a gradual decrease in bacterial adsorption. The extent of bacterial adsorption strongly depended on the nature of the metallic substratum and decreased accordingly as follows: platinum > titanium > stainless steel > aluminum alloy > carbon steel > copper. Adsorption on all tested metals was approximately two orders of magnitude higher with the relatively more hydrophobic F. breve compared to the less hydrophobic P. fluorescens P17. The effect of electrochemical polarization on the initial stages of bacterial adsorption onto metallic substrata is further discussed.

Biodeterioration of dental materials: Influence of bacterial adherence

The aim of this work was to carry out a comparative study of microbial adhesion on dental alloys and glass ionomers that release fluoride. The action of NaF on the early stages of biofilm development and on the corrosion of the metallic dental materials was analysed. Open circuit potential measurements and potentiostatic electrochemical techniques with different perturbation programs as well as SEM observations, and optical and epifluorescence microscopy were employed. A notable effect of topography and the nature of the substratum on bacterial distribution was observed. In addition, changes in the density and thickness of microbial colonies were noticed when fluoride was present. The results show that the antimicrobial effect of fluoride was significant against planktonic but not against sessile microorganisms. Fluoride released by glass ionomers did not impede bacterial adhesion to the surface. With respect to corrosion, fluoride did not alter significantly the passivity of the dental metallic biomaterials assayed, except for Cu‐Al alloy. Titanium dissolution could occur at high fluoride concentrations (8gl‐1) during oxide layer formation. Consequently, bacterial adherence was influenced by the nature and topography of the substratum and by the presence of fluoride which could also affect the electrochemical behaviour of some metallic substrata.

Use of dissolved ozone for controlling planktonic and sessile bacteria in industrial cooling systems

Cooling water treatment requires effective, environmentally-safe biocides compatible with system operation. The unique combination of high biocidal activity during use with no toxic discharge, could render dissolved ozone a safe biocide for cooling water treatment. Planktonic and sessile cells of Pseudomonas fluorescens (a frequent microbial contaminant of industrial systems) were used in this work to assess the biocidal effectiveness of ozone. Dissolved ozone showed to be effective at concentrations between 0.1 and 0.3 ppm, to eliminate completely the levels of planktonic cells used in this paper (10 7–10 8 cell/ml) within a range of contact times between 10 and 30 min. However, ozone at 0.15 ppm was only able to diminish sessile cell population by two or three orders of magnitude. This minor biocidal effectiveness of ozone against bacterial biofilms is discussed in this paper, taking into account recent concepts on structure and dynamics of biofilms. Different metallic substrata were assayed to verify if there was any effect of metal nature on the biocidal action. Open circuit potentials vs. time experiments and potentiodynamic polarization curves were made for assessing the effect of dissolved ozone on the corrosion behavior of the metals tested.

Die Schwingquarzmethode

AbstractIn the last decade, the Quarz Crystal Micro Balance has proved its enormous capability to be suitable to a wide range of applications in thc fields of chemistry, physics, materials and surface science, maritime and medical research as well as in sensor technology. The physical basis of these features are mega Hertz shear oscillations which create oscillatory movements at the solid/liquid junction. They give rise to an acceleration which sur‐ passes the acceleration of gravity by several orders of niagnitude. These unique movement conditions allow, besides the well known mass sensitivity of several nanograms, nanotribologic investigations between metallic substrata and monolayer deposits of foreign materials. It senses grain size effects in metallic deposits and allows the complete determination of the complex and anisotropic shear compliance of thin polymer layers. With a structured oscillator surface density and viscosity of a liquid phase can be determined independently. It also allows monitoring of chemical reactions with a time resolution &lt; lms.

Biocidal action of ozone against planktonic and sessile Pseudomonas fluorescens

The efficacy of ozone biocidal action against planktonic and sessile Pseudomonas fluorescens was studied using different contact times and biocide concentrations. Bacterial biofilms were formed on different metallic substrata frequently used as structural materials in industrial installations. The results showed that the biocidal action of ozone against planktonic cells can be represented by a dose‐response relationship in which the contact time factor was more significant than the concentration. The efficacy of ozone against sessile bacteria was lower than that found for planktonic cells. Turbulent flow significantly improved the inactivation rate, suggesting that a diffusional impediment was involved in the mass transfer process. However, diffusional resistance alone cannot explain the observed decrease in biocidal efficacy. Ozone penetration into the biofilm appeared to be a function of simultaneous diffusion and a reaction of the biocide in the biofilm matrix; the latter may be the result of microscale differences in biomass distribution as well as hydrodynamic conditions. In addition, oxidation by‐products may contribute an additional resistance to ozone diffusion, which may be even higher than that of the biofilm itself.

Electrochemical Behaviour of Four Lacquers for Tomato Cans

20% of the overall production of Italian canmakers is intended for tomato products. In recent years the use of internal lacquered cans has continued to increase, both for commercial reasons and for greater guarantee of quality. The study of the interaction between the product and the container (which couples a metal with an organic coating) is of immense practical interest, because of the effect this interaction has on the shelf-life of canned tomatoes. In our experimental work we examined four types of commercial lacquer covering five different metal substrata, four tinplates and one tin free steel. In the first stage of our study we examined the corrosion resistance of each of the lacquering systems by placing them in a solution simulating tomato products (made with citric acid) and using electrochemical impedance spectroscopy. The corrosion resistance of each system was significantly different: the electrochemical parameters of the organosol lacquer (lowest coating capacitance (Cc) and highest pore resistance (Rp) denote that this lacquer has good barrier properties and indicate that corrosion occurs upon small areas (high value of Rp) and slowly. The white lacquer showed the lowest resistance to lacquer delamination (high value of double layer capacitance (Cdl) immediately after 500 hours of contact), while the epoxyphenolic lacquer gave an intermediate performance. In the second stage of the work we studied the influence of the mechanical stress resulting from the formation of the body beads upon the corrosion resistance of the four lacquering systems. In each case, proceeding from the sheet material to the can body, the impedance value decreased two-fold; with the organosol lacquer continuing to show better barrier properties. The degree of corrosion of the can body is influenced by the type of can end to which the body is galvanically coupled. The higher the impedance of the can ends, the lower the corrosion of the can body.

Instrumental analysis of microbiologically influenced corrosion

Appropriate application of techniques for detection andmonitoring of microbiologically influenced corrosion isessential for understanding the mechanistic nature of theinteractions and for obtaining control methods. This paperreviews techniques and methods applied tomicrobiologically influenced corrosion in recent years.The techniques presented in this paper includeelectrochemical noise measurement, concentric electrodes,scanning vibrating electrode mapping, electrochemicalimpedance spectroscopy, atomic force microscopy,confocal laser microscopy, Fourier transform infraredspectroscopy, x-ray photoelectron spectroscopy, Augerelectron spectroscopy, extended x-ray absorption finestructure and utilization of piezoelectric materials. Thesetechniques are reviewed regarding the heterogeneouscharacteristics of microbial consortia and their possibleinfluences on metal substrata. We hope this review willmotivate application and combination of new techniquesfor practical detection and on-line monitoring of theimpact of biofilms on engineering alloys.

Formation of intermediate intermetallic layers on interaction of electrodeposited Sn, Ni-Fe, Ni-B coatings with different metallic substrata

The structure of layers and formation of intermetallic phases after thermal treatment in the system of thin electrodeposited Sn, Ni-Fe and sputtered Cu, Fe-Ni layers (thickness 0.1-2.0 μm) and thick electrodeposited Sn (thickness 6-10 μm) and Fe-Ni and Ni-B layers (thickness 2 μm) have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and by metallographic and X-ray diffraction (XRD) techniques. The formation of intermetallic phases NiSn3, Ni3Sn2, FeSn2 and considerable reduction in the formation of brittle layers Ni3Sn4, Cu6Sn5, Cu3Sn are determined by the structure and purity of electrodeposited tin [C (0.5-5) x 10-2; N (1-5) x 10-2; Fe, Cu, Bi, Pb (0.15-5.0) x 10-2 wt%] in the system Sn/Fe-Ni/Cu. Electrodeposited Fe-Ni (80% Ni) as barrier layer in the system Sn/Fe-Ni/sputtered Cu completely prevents formation of Cu6Sn5, Cu3Sn as a result of thermal treatment at 170°C up to 75 h. An amorphous Ni-B layer [B 4-8; C (3-7) x 10-2 wt%] prevents formation of Ni3Sn4 and Cu6Sn5 in the system Sn/Ni-B/Cu (or Cu-Zn alloy) as a result of thermal treatment at 130°C (200 h) and 170°C (150 h).

Organic coatings for marginally prepared steel surfaces

The present study, carried out in the frame of a common research programme between the Institute of Chemistry, Faculty of Engineering at the University of Genoa and AGIP CORM Department about alternative surface preparation methods, is a preliminary contribution to the development of a series of rust-prevention coatings that can be applied directly in order to protect steel structures exposed to aggressive environments. The use of ‘rust converters’ may be considered a tool for alternative surface preparation but it is necessary to control the amount of loose rust layers and to ensure their complete removal. The poor adhesion level of converted layers is a problem not yet solved and it does not allow for a subsequent coating and/or finishing step. The application of the ‘surface tolerant’ coating systems seems to be a more useful way to protect steel structures without sandblasting and all its related economic and environmental disadvantages. The application of these systems on marginally prepared steel surfaces shows promising reliability both for the intrinsic protective power and for the adhesion to the metallic substrata. Their use during repainting maintenance is a reliable proposition and a profitable way to overcome not only technical problems but also subsequent environmental pollution and related constraints.

Effects of various metal substrata on accumulation ofPseudomonas aeruginosabiofilms and the efficacy of monochloramine as a biocide

Monochloramine at 4 mg·l−1 was used to treat biofilms of Pseudomonas aeruginosa grown in annular reactors on various metal substrata, including stainless steel, mild steel and copper. Disinfection of in situ biofilms was most efficient on the stainless steel slides. The treatment reduced viable cells in the biofilm on the stainless steel slides by more than 4 orders of magnitude after 60 min, while the same treatment reduced viable cells in the biofilms on the other slides (mild steel and copper) by only 2 orders of magnitude. Mild steel corrosion products retarded the disinfection of homogenized biofilm cells. The composition of steady state biofilms on the various substrata (before biocide treatment) differed. Biofilm on stainless steel slides had more viable cells but less extracellular polymeric substance (EPS). Biofilms on mild steel and copper slides had fewer viable cells but more EPS. Almost 95% of total cells in the biofilm on the copper slides were dead cells. The lower efficacy of disinfection ...

Biofilms and the survival of opportunistic pathogens in recycled water

Microorganisms are likely to develop an organic film on pipes, water reservoirs and filters used for waste water reclamation during extended missions in space. These biofilms can serve to protect and concentrate potentially pathogenic microorganisms. Our investigation has emphasized the survival strategy of opportunistic pathogenic bacteria in distilled water. Pseudomonas aeruginosa and Staphylococcus aureus were used as test organisms. Cultures were incubated at 10 °, 25 ° and 37 °C. No viable Staphylococcus cells were detected after the first week of incubation. P. aeruginosa, however, survived in distilled water up to 5 months at all three temperatures tested. The starved cells were able to form a biofilm layer on stainless steel. The cells exhibited a negative surface charge. The charge may be involved in the adhesion of this bacterium to metal substrata. We are currently investigating the importance of adhesion in the survival of this and other potential human pathogens found in water recycling systems.