Characterization of corrosion behavior of aluminum welds reinforced with copper powder

This paper reports on the corrosion behavior of aluminum metal inert gas (MIG) welds reinforced with copper powder particles. Pure aluminum, AA1100 sheets, machined to a 45° v-grooved were used for this experiment. Copper powder particle reinforced samples and unreinforced samples were investigated. The corrosion behavior of the samples were investigated in 3.5 % sodium chloride (NaCl) solution, using the potentiodynamic polarization technique. The results revealed that the corrosion resistance for reinforced samples were higher than those for unreinforced samples. Hence the corrosion resistance of aluminum AA1100 welds can be improved by the addition of copper powder particle in the weld seam, and it is therefore recommended for typical industrial applications.     

Corrosion behaviour and galvanic coupling with steel of Al-based coating alternatives to electroplated cadmium

The galvanic corrosion behaviour of bare steel coupled to steel with an Al–Zn flake inorganic spin coating, an Al-based slurry sprayed coating, an arc sprayed Al coating and electroplated cadmium has been investigated. The sacrificial and galvanic behaviour of the coatings was studied in 3.5 wt. % NaCl solution using open-circuit potential, potentiodynamic polarisation and electrochemical noise measurements. The coatings were characterised by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Experimental results showed that the Al-based slurry sprayed coating exhibited an open-circuit potential closer to the steel substrate than other coatings, as well as a low corrosion current density and a more positive corrosion potential. In terms of the galvanic suitability of the investigated coatings for the steel substrate, both the Al–Zn flake inorganic spin coating and the Al-based slurry sprayed coating show low galvanic current, in comparison with the arc sprayed Al coating and electroplated cadmium. This behaviour confirms their superior cathodic protection capability and galvanic compatibility over other coatings tested. Electrochemical noise measurements provide accurate information on the coatings' galvanic behaviour, which can be complimented by the data obtained from superposition of potentiodynamic corrosion scans of the coating and bare steel, provided that the corrosion potential difference between the two materials does not exceed 300 mV.     

Pitting corrosion resistance of laser surface alloyed 304 stainless steel

Abstract

The pitting corrosion resistance of AISI 304 stainless steel (SS), which was laser melted in both nitrogen and argon atmosphere, was studied using the potentiodynamic anodic polarisation method. An attempt was made to introduce nitrogen onto the surface layers by melting in nitrogen atmosphere and argon atmosphere using a continuous wave CO₂ laser as the heat source at a power output of 3·06 kW at the laser head. The pitting corrosion resistance was determined by measuring the critical pitting potential during anodic polarisation. Secondary ion mass spectrometry (SIMS) was carried out on the laser melted surface to characterise the chemical composition. It was found that the pitting corrosion resistance of 304 SS was improved when laser surface melting was carried out in argon and was improved further when melting was carried out in nitrogen atmosphere. However, the improvement in pitting corrosion resistance in laser melted material was observed only in the reabraded condition and the pitting corrosion resistance in the as melted condition was lower than for the unmelted 304 SS. The improvement in localised corrosion behaviour was attributed to the increase of nitrogen content which was incorporated onto the surface layer during laser surface melting and this was confirmed using SIMS.

MST/1530     

Influence of size and volume share of WC particles on the properties of sintered metal matrix composites

Steel matrix composites are being increasingly investigated because of their wear and corrosion properties, allowing their wide application in various industrial sectors. The interaction of tungsten carbide (WC) with the steel matrix, including an analysis of its volume share and particle size, is crucial in determining the resistance to wear and corrosion of the metal matrix composite (MMC). However, there is little information in the literature about sintered MMCs based on low-alloy steels. This paper presents the results of an analysis of the influence of the volume share of WC (5?vol.% and 20?vol.%) and carbide particle size (0.7?µm and 5.0?µm) on the resistance to abrasion of a friction pair: sintered composite and bearing steel, analysed using two rotational speeds (0.02?m/s and 0.2?m/s). Moreover, the resistance to corrosion in 3.5% NaCl solution is also characterized. It is shown that both the volume share and the size of the WC particles used as reinforcement of the steel matrix have a significant impact on the densification behaviour as well as the resistance to abrasive wear and corrosion of sintered MMCs based on low-alloy steel.     

Influence of laser surface alloying with chromium and nickel on corrosion resistance of type 304L stainless steel

Abstract

The influence of laser surface alloying (LSA) with Cr and Cr + Ni on the corrosion behaviour of type 304L stainless steel (SS) was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in chloride (0·5M NaCl) and acidic (1 N H₂SO₄) media. Surface alloying was carried out by laser cladding type 304L SS substrate with premixed powders of AISI type 316L SS and the desired alloying elements. The results indicated that Cr surface alloyed specimen exhibited a duplex (γ + α) microstructure with Cr content of ～24 wt-%, whereas Cr + Ni surface alloyed specimen was associated with austenitic microstructure with Cr and Ni contents of ～22 wt-% each. The potentiodynamic polarisation results in chloride solution indicated that LSA with Cr + Ni considerably enhanced the pitting corrosion resistance compared with LSA with Cr alone. In acidic media, such beneficial effects were not observed. Electrochemical impedance spectroscopy results showed an increase in semicircle arc for both chloride and acidic media for both Cr and Cr + Ni clad samples indicating improvement in the oxide film stability compared with untreated specimen. The polarisation resistance was higher and capacitance values of the laser clad specimen were lower than those in the untreated specimen. The microstructural changes and compositional variations produced by LSA are correlated to the corrosion behaviour.     

Neuentwicklungen für den Verschleiß‐ und Korrosionsschutz beim Plasma‐Pulver‐Auftragschweißen

New developments for wear an corrosion protection by weld surfacing with plasma transmitted arc process Highly wear‐resistant claddings which contain carbides can be applied by weld surfacing with the PTA process. The use of vanadium carbide prevents undesirable reactions with the matrix material. Thus, highly corrosion‐resistant Fe‐based claddings can be produced for applications in the food and marine industries, and Ni‐based claddings can be applied to components exposed to inorganic acid attack. A combined test is applied for determining the relative effect of corrosion under combined exposure to abrasive wear and corrosion and indicates the primacy of abrasive wear for behaviour in operation.     

A100钢低氢脆刷镀镉镀层海洋环境腐蚀行为研究

通过海洋环境下的户外暴露实验研究了A100钢表面低氢脆刷镀镉的腐蚀行为及腐蚀对力学性能的影响。通过腐蚀动力学曲线反映了镀层腐蚀失重的变化,并利用交流阻抗技术表征了镀层在不同腐蚀阶段的特征。结果表明:镀层具有很好的耐腐蚀性能,但随着实验的进行腐蚀速率逐渐加快;腐蚀对镀层力学试样的力学性能影响很大,导致抗拉强度降低,断口呈氢脆断裂。     

Influence of nitriding on corrosion resistance of martensitic X17CrNi16‐2 stainless steel

Nitriding increases surface hardness and improves wear resistance of stainless steels. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 °C and 525 °C and salt bath nitrocarburizing were carried out on X17CrNi16‐2 stainless steel. Microhardness profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were preformed by X‐ray diffraction (XRD) and glow‐discharge optical emission spectrometry (GD‐OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNi16‐2 steel.     

A filiform corrosion and potentiodynamic polarisation study of some aluminium alloys

The aim of the present investigation is a combined study of filiform corrosion of aluminium alloys by accelerated exposure tests and potentiodynamic polarisation measurements. The accelerated exposure tests are performed on binary Al-Cu, Al-Mg, Al-Si and Al-Zn model alloys, a ternary Al-MgSi alloy and on the two commercial alloys, AA2024-T351 and AA7075-T651, with variations of composition and surface treatments. The surface treatments cover simple degreasing, chromate and cerium based treatments. A trend of a higher filiform corrosion susceptibility with increasing alloying elements concentrations was observed for all model systems. Furthermore, the filiform corrosion susceptibility varies with the solute atom, in particular Cu was found to have a detrimental effect on the filiform corrosion properties. Both chromating and cerating improve the filiform corrosion resistance of the alloys significantly. To explain the trends observed in the exposure tests, polarisation measurements were performed on the untreated Al-Cu and Al-Zn alloys in bulk anolyte and catholyte solutions which are characteristic for the local anodic and cathodic sites in the filaments on the aluminium substrates. From these measurements a filiform corrosion current, defined as the intercept of the anodic and cathodic curves, can be determined. The present set of experiments shows a correlation between the filiform corrosion properties during accelerated exposure tests and the potentiodynamic polarisation measurements for the Al-Cu alloys. When comparing the results for the Al-Cu and Al-Zn binary alloys it can be concluded that the correlation factor differs significantly with the solute atom and the filiform corrosion current proves to be a non-uniquely discriminating parameter for the filiform corrosion susceptibility of the model alloys. The difference in correlation factor for the Al-Cu and Al-Zn alloys is attributed to differences in the electrochemical behaviour of these alloys with local variations in substrate composition. For the Al-Cu and Al-Zn model alloys the filiform corrosion initiation characteristics are related to the passive range and thus implicitly to the ease of pitting of the alloy. A smaller passive range corresponds to a higher filiform site density for both the Al-Cu and Al-Zn alloys.     

Strain Profiling of a Ferritic‐Martensitic Stainless Steel Sheet — Comparing Synchrotron with Conventional X‐Ray Diffraction

To improve the fatigue resistance of stainless steel sheet, it is a common practice to induce compressive residual stress in the surface through shot‐peening or tumbling. Stress depth profiles obtained by tumbling of thin stainless steel tensile rods were analysed using laboratory and synchrotron X‐Ray Diffraction (XRD). Both the non‐destructive synchrotron and the laboratory XRD etch‐depth profile gave similar results: a residual stress profile decaying over a depth not exceeding 50 µm into the material.     

Combined Impact of Ultraviolet and Chemical Fluids on High‐density Polyethylene Packaging Material

To investigate the ageing behaviour of filled plastic containers outdoors, square cuts of the wall of two high‐density polyethylene (HDPE) types were exposed to ultraviolet (UV) radiation at their front side and to specific liquid chemicals (de‐ionized water, surfactant or White Spirit) at their back. The UV radiant exposure at the front side was 80 MJ/m². To compare the actions of the different exposures, separate dark backside fluid exposures were performed, in parallel. Besides, UV weathering was carried out until a UV radiant exposure of 325 MJ/m², being roughly comparable to outdoor exposure of one year in Northern Australia. An unpigmented HDPE included in the investigation gave no sufficient protection for the White Spirit. In addition, it showed clear degradation after several of these exposures. In combination with the White Spirit, an increase of carbonyl bonds was measured, presumably assignable to degradation products of the White Spirit. For a pigmented HDPE material, with the implemented combined exposures, no relevant damage was observed, within applied the exposure period. Copyright © 2011 John Wiley & Sons, Ltd.     

Corrosion behaviour of Al 1050 severely deformed by rotary swaging

In this study, corrosion behaviour of ultrafine-grained (UFG) commercial pure aluminium Al 1050 processed by rotary swaging (RS) was examined using potentiodynamic polarization and weight loss immersion test in 3.5% NaCl solution. Corrosion behaviour of UFG Al 1050 was compared with that of coarse grained (CG) as-received material. The results showed that ultrafine grain refinement by RS led to marked improvement of the corrosion resistance. The improvement in corrosion resistance is profited from the denser and stable passive film due to more grain boundaries, larger fraction of non-equilibrium grain boundaries and residual stress of the UFG pure aluminium. The weight loss tests revealed low corrosion rate values of RS material compared to CG as-received material. Scanning electron microscopy (SEM) analysis revealed a higher number of rectangular shallow pits (more close to patches of general dissolution); larger pits size was observed in the as-received compared to RS materials.     

Mechanical properties and corrosion behaviour of developed high nitrogen high manganese stainless steels

Influence of composition, specifically manganese and nitrogen content, on the microstructure associated corrosion resistance property of newly developed stainless steel has been studied. The developed steels have been characterised for their microstructure, mechanical and electrochemical properties. The results indicate that the addition of manganese and nitrogen as a substitute for nickel favours the austenite microstructure, higher yield strength (>350 MPa), tensile strength (>700 MPa), elongation and superior Charpy V-notch impact toughness properties. The results obtained from electrochemical tests such as potentiodynamic polarisation and electrochemical impedance spectroscopy of manganese stainless steel show remarkable improvement (about 4 times) in corrosion resistance exhibiting passivity behaviour like that of commercial stainless steel (316L).     

Bioinspired Mechanically Robust Metal‐Based Water Repellent Surface Enabled by Scalable Construction of a Flexible Coral‐Reef‐Like Architecture

Mechanical robustness is a central concern for moving artificial superhydrophobic surfaces to application practices. It is believed that bulk hydrophilic materials cannot be use to construct micro/nanoarchitectures for superhydrophobicity since abrasion‐induced exposure of hydrophilic surfaces leads to remarkable degradation of water repellency. To address this challenge, the robust mechanical durability of a superhydrophobic surface with metal (hydrophilic) textures, through scalable construction of a flexible coral‐reef‐like hierarchical architecture on various substrates including metals, glasses, and ceramics, is demonstrated. Discontinuous coral‐reef‐like Cu architecture is built by solid‐state spraying commercial electrolytic Cu particles (15–65 µm) at supersonic particle velocities. Subsequent flame oxidation is applied to introduce a porous hard surface oxide layer. Owing to the unique combination of the flexible coral‐reef‐like architecture and self‐similar manner of the fluorinated hard oxide surface layer, the coating surface retains its water repellency with an extremely low roll‐off angle (<2°) after cyclic sand‐paper abrasion, mechanical bending, sand‐grit erosion, knife‐scratching, and heavy loading of simulated acid rain droplets. Strong adhesion to glass, ceramics, and metals up to 34 MPa can be achieved without using adhesive. The results show that the present superhydrophobic coating can have wide outdoor applications for self‐cleaning and corrosion protection of metal parts.     

N-benzyl-N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine as corrosion inhibitor of steel in 1 M HCl

The inhibition effect of a new bipyrazole derivative namely N-benzyl-N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine (BBPA) on the corrosion of steel in 1 M HCl is studied at 308 K. Weight-loss measurements, potentiodynamic polarisation, linear polarisation and impedance spectroscopy (EIS) methods were used. Results show that BBPA is a good inhibitor and inhibition efficiency reaches 87% at 5 · 10^− 4 M. The values of the inhibition efficiency calculated from these techniques are reasonably in good agreement. Polarisation curves revealed that this organic compound acts as a mixed-type inhibitor. The temperature effect on the corrosion behaviour of steel in 1 M HCl with and without BBPA at 5 · 10^− 4 M is studied in the temperature range 308-353 K. The associated activation energy is determined. The adsorption of BBPA on the steel surface obeys to the Langmuir's adsorption isotherm. EIS measurements show that the transfer resistance increases with the inhibitor concentration. Efficiency is explained by the theoretical studies.     

Herstellung,Mikrostruktur und Korrosionsverhalten der konventionellen und ultrafeinkörnigen Legierung EN AW‐6082

Fabrication, microstructure and corrosion behaviour of the conventional and ultrafine‐grained AA6082 The effect on the corrosion behaviour of the commercially available AlSi1MgMn alloy (AA6082) with ultrafine grains in comparison to coarse grains, i.e. the conventional material state was investigated. The results of the electrochemical experiments are presented in correlation to the microstructure before and after the corresponding examinations. The quantification of the induced corrosion damage as well as the corrosion characteristics shows the reduced susceptibility of the material with ultrafine‐grained microstructure in contrast to the coarse‐grained initial state.     

Influence of nitrogen addition on the crevice corrosion resistance of nitrogen-bearing austenitic stainless steels

Crevice corrosion studies were carried out on nitrogen-bearing types 304, 316 and 317 austenitic stainless steels (SS) by a potentiodynamic anodic polarisation method in an acidic chloride medium. A special all-glass crevice assembly was used for providing reproducible crevice effects on the surface of the test specimen. The results indicated that the increase in nitrogen content improved the crevice corrosion resistance of the alloys by decreasing the active dissolution, and increasing both passive film stability and the potential at which crevice attack was stable. This was very significant for 304 and 316 SS alloys in comparison with 317 SS alloys. The combined influence of nitrogen and molybdenum was found to be very significant in providing high crevice corrosion resistance for 317 SS alloys. Optical microscopic observation revealed severe crevice attack on types 304 and 316 SS alloys compared to mild crevice attack on type 317 alloys. Based on the results of the present investigation a possible mechanism by which nitrogen addition improved the crevice corrosion resistance is discussed.     

Electrochemical behaviour of Ti–25Nb–3Mo–3Zr–2Sn biomedical alloy in different simulated physiological environments

The electrochemical corrosion behaviour of biomedical Ti–25Nb–3Mo–3Zr-2Sn (TLM) alloy was investigated in various simulated body fluids at 37±0·5°C utilising potentiodynamic polarisation and current–time curves. The Ti–6Al–4V (TC4) alloy was also investigated to make a comparison. The different simulated body fluids comprised of 0·9%NaCl saline, Hank’s and Ringer’s solution were employed. The effect of heat treatment on the electrochemical behaviour of the TLM alloy was also considered. It was discovered that all the test specimens were passivated once immersed into the simulated body fluids. It was also found that the TLM alloy has poorer corrosion resistance in Hank’s solution, due to the chemical composition of the Hank’s. After different heat treated, the TLM alloy had different phases and microstructure, and the corrosion behaviour of the TLM alloy was different. In this study, after the heat treatment of 760°C/1 h/AC+550°C/6 h/AC, the TLM alloy had better corrosion resistance. Owing to the corrosion resistance of the TLM alloy was influenced by numerous factors, such as microstructure and the chemical composition of electrolyte, the corrosion behaviour of the TLM alloy is complex. By comparing with the corrosion behaviour of the TC4 alloy, the TLM alloy has poorer corrosion resistant than the TC4 alloy under the same conditions. But the current–time curves of the TLM alloy were more stable than these of the TC4 alloy with further experiments, because of the more passivation film on the surface of the TLM alloy.     

Development of corrosion protective polymeric coatings from a non‐edible seed oil

In this study, we have developed corrosion protective coatings material from Pongamia glabra seed oil. First, oil was converted to pongamia oil epoxy (POE). The resin was synthesized by the reaction of POE with phthalic acid to develop polyester (PE) and further treated with diethylene triamine (DTA) in different (20–35%wt) amount. The structural elucidation of POE and PE were carried out by FT‐IR, ¹H‐NMR and ¹³C‐NMR spectroscopic techniques. Thermal behavior of PE‐30 was studied by thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC). The coatings of PE‐DTA resins were prepared on mild steel strips to investigate their physico‐mechanical and corrosion performance. Corrosion protection of coated panels were examined in different corrosive media (3.5 wt% HCl, 3.5 wt% NaOH, 5.0 wt% NaCl) using potentiodynamic polarization and AC impedance. Thermal analyses revealed that PE‐30 may find application as eco‐friendly corrosion protective coating safely used up to 175°C.     

Ausscheidungs- und Versprödungsverhalten nickelhaltiger Superferrite

Precipitation and embrittlement behaviour of nickel containing Superferrites During the last years high chromium ferritic stainless steels socalled Superferrites have become of general interest since the mean disadvantages of these steel grades, namely cold brittleness and susceptibility to intergranular corrosion, can be avoided by means of new melting techniques. This group of steels show remarkable strength properties and excellent corrosion behaviour especially in chloride containing solutions. Because of the high content of alloying elements the ferritic solid solution is supersaturated, so that precipitation and embrittlement can occur. From 950° to 550 °C the brittle Chi- and/or Sigmaphase can be precipitated, at temperatures below 550 °C the material can fail by the socalled 475°-embrittlement. Additions of nickel and stabilising by titanium enhance the precipitation process well as the 475°-embrittlement, while a columbium stabilisation of the present carbon and nitrogen contents up to 150 ppm shows no influence. Within the investigated alloying range with 20 to 28% Cr, up to 5% Mo and up to 4% Ni the columbium stabilised steel with 28% Cr, 2% Mo and 4% Ni results as the optimal combination referring to its technological properties as well as to its precipitation and embrittlement behaviour.