Effects of temperature and operation parameters on the galvanic corrosion of Cu coupled to Au in organic solderability preservatives process

In this work, we quantitatively examined the effects of temperature and operation parameters such as anode (Cu) to cathode (Au) area ratio, stirring speed, and Cu ion concentration on the galvanic corrosion kinetics of Cu coupled to Au (i_couple (Cu-Au)) on print circuit board in organic solderability preservative (OSP) soft etching solution. With the increase of temperature, galvanic corrosion rate (i_couple (Cu-Au) was increased; however, the degree of galvanic corrosion rate (i_couple (Cu-Au) - i_corr (Cu)) was decreased owing to the lower activation energy of Cu coupled to Au, than that of Cu alone. With the increase of area ratio (cathode/anode), stirring speed of the system, i_couple (Cu-Au) was increased by the increase of cathodic reaction kinetics. And i_couple (Cu-Au) was decreased by the increase of the Cu-ion concentration in the OSP soft etching solution.     

Galvanic corrosion of Cu coupled to Au on a print circuit board; Effects of pretreatment solution and etchant concentration in organic solderability preservatives soft etching solution

In present study, we quantitatively define the galvanic corrosion phenomenon of Cu electrically coupled to Au on Print Circuit Board in Organic Solderability Preservatives (OSP) pretreatment (pickling and soft etching) solutions. As a result of polarization and ZRA test, galvanic corrosion rate of Cu in soft etching solution was about 3000 times higher than that of pickling solution. The oxone in OSP soft etching solution was acted as strong oxidant for Cu on PCB substrate. And the galvanic corrosion of Cu in OSP soft etching solution was examined with the change of etchants (oxone (KHSO₅), sulfuric acid (H₂SO₄)) concentration. The galvanic corrosion rate of Cu was increased by the increase of the oxone and sulfuric acid concentrations, which lead to the increase of cathodic reactant such as HSO ₅ ^- and H⁺ ions. And the degree of galvanic corrosion rate of Cu (Δ_{isoft etching} = i_{couple, (Cu-Au)} - i_{corr, Cu}) decreased with the decrease of the oxone and sulfuric acid concentrations.     

Preventing or accelerating galvanic corrosion through the application of a proper external magnetic field

The effect of an external magnetic field on the corrosion behaviour of a galvanic couple, zinc (Zn)–stainless steel (SS 316L), has been investigated in a 0·055 mol L^?1 potassium chloride (KCl) solution. The impact of the orientation as well as the magnetic flux density B (Wb m^?2) on the corrosion progression of the galvanic couple, is evaluated heuristically by monitoring the corrosion potential E_corr (mV) and the current density I_corr (μA cm^?2) of the system. A strong influence of the magnitude and orientation of the magnetic field on the Zn–SS316L galvanic couple corrosion was observed, whereas the field was proven to act either protective or accelerating in terms of corrosion.     

Fast etching of copper in thionyl chloride/acetonitrile solutions

We report fast etching of copper (Cu) in thionyl chloride (SOCl₂)/acetonitrile (CH₃CN) solutions. The etching rate can be tuned over a wide range by varying the concentration of the etchant, and the stirring rate of the liquid. The etching rate reaches 36 mg min⁻¹ cm⁻² in 1 mol L⁻¹ SOCl₂/CH₃CN under stirring at room temperature, which is much faster than any currently used etchant for Cu. With sonication, the etching rate reaches 320 mg min⁻¹ cm⁻². The chemical reactions involved are studied by X-ray photoelectron spectroscopy and Raman spectroscopy. The fast etching may find important applications in microelectronics.     

Untersuchung über die Auswirkung der Elementbildung zwischen Stahl in Beton und Stahl in Erdboden

Investigation of the effect of galvanic corrosion between steel in concrete and steel in soil The investigation of cathodic polarization of steel in concrete on samples of portland cement and blast furnace cement revealed that oxygen reduction on steel in portland cement is less hindered than on steel in blast furnace cement. As to the magnitude of the cathodic current the aeration of the samples is important. Dry stored samples before measuring case a higher current density than wet stored ones. A significant relationship of the cathodic current depending on the water/cement value and the storage time of concrete could not be ascertained. The polarization resistances for portland cement samples lie within 86 and 3000 kΩ · cm² and for blast furnace cement samples between 430 and 5100 kΩ · cm². The measurements of the anodic current densities on corrosion cells of steel in concrete/steel in solution and steel in wet sand respectively rendered, by varying the cathode/anode aspect ratio from 1000: 1 to 1: 1, values for portland cement samples between 560 and 1,2 μAJcm² (corresponding to an annual corrosion of 6,5 and 0,014 mm respectively), and for blast furnace cement samples values between 730 and 0,28 μA/cm² (corresponding to an annual corrosion rate of 8,5 and 0,003 mm respectively). A decrease of the anodic current density variable with time could not be observed during the 28 days of measurements. On account of the investigations the following conclusions can be made: A formation of a corrosion cell with steel in concrete/steel in soil is particularly then to be expected if the concrete is dry on one side, e.g. the foundation of a building where oxygen diffuses by way of the gas pores in the concrete from the inner side to the cathode. This is less serious if the concrete is fully embedded in soil and thoroughly moistened. In this case the transport of oxygen has to be carried via waterfilled pores.     

Korrosion von silber in neutralen alkalisulfatschmelzen

The corrosion of silver in the ternary eutectic of (mole %) 78 Li₂SO₄, 13·5 K₂SO₄ and 8·5 Na₂SO₄ at 625°C is proportional to the oxygen pressure above the melt. The corrosion current density of completely immersed specimens is 1·4 × 16^?6 A cm^?2 in the unstirred melt under a 100% oxygen atmosphere. The corrosion rate is increased by stirring.Specimens incompletely immersed in the melt are corroded at a much higher rate than fully immersed specimens. The specimen surface protruding from the melt is covered by a thin film of the molten material. Local cells are formed where O₂ is preferentially reduced on the surface above the melt, and silver is preferentially dissolved from the immersed portion of the surface. The corrosion current density is controlled by the ratio of areas inside and outside the melt.     

Evaluation of nanometer-sized zirconium oxide incorporated Al—Mg—Ga—Sn alloy as anode for alkaline aluminum batteries

Zirconium oxide nanoparticles with 0.4 wt.% and 0.8 wt.% are incorporated into the Al—0.65Mg—0.05Ga— 0.15Sn (wt.%) alloy anode (base alloy) in order to improve the performance of the resulting anodes. Electrochemical characterization of the reinforced alloys was done by potentiodynamic polarization, electrochemical impedance spectroscopy and galvanostatic discharge and corrosion behavior was evaluated using self-corrosion rate and hydrogen evolution in 4 mol/L KOH solution. The surface morphology of the alloys was also studied using field emission scanning electron microscope (FESEM). The obtained results indicate that the base alloy shows high corrosion rate in 4 mol/L KOH solution by releasing 0.47 mL/(min·cm²) hydrogen gas, whereas the alloy containing 0.8 wt.% ZrO₂ provides the lowest hydrogen evolution rate by releasing 0.32 mL/(min·cm²) hydrogen gas. Furthermore, by increasing zirconium oxide nanoparticles, the corrosion current density of the aluminum anodes is decreased and their corrosion resistance increases significantly compared to the base alloy in alkaline solution. In addition, nanometer-sized zirconium oxide incorporated anodes exhibit the improved galvanic discharge efficiencies, so that 0.8 wt.% nano-zirconium oxide incorporated base alloy displays the highest power density and anodic utilization compared with the others in 4 mol/L KOH solution.     

Enhanced corrosion resistance of Zn–Cu–Ti alloy with addition of Cu–Ti amorphous ribbons in 3.5% NaCl solution

In the present study, Zn–0.3Cu–0.3Ti alloy (sample I) was fabricated by a simple low-temperature melting method using Cu–50Ti amorphous alloy ribbons for corrosion in 3.5% NaCl solution. As a comparison, crystalline Cu–50Ti master alloy was used to prepare Zn–0.3Cu–0.3Ti alloy (sample II). Sample I comprising Zn, TiZn₃, and TiZn₁₅ phases exhibits an equiaxed microstructure with subgrain structure. Large TiZn₃ particles show cluster feature, whereas intermittent small TiZn₁₅ particles exist at grain boundaries and subgrain boundaries. In sample II, the Zn matrix with typical dendritic microstructure is observed and no large particles are found. Compared with sample II, sample I shows lower weight gain and corrosion current density and a higher slope of cathode polarization curve. The weight gain for sample I is only 0.59 mg·cm⁻², but for sample II, this value reaches 0.70 mg·cm⁻². After 8 days of corrosion, corrosion products are mainly Zn₅(OH)₈Cl·H₂O and ZnO, showing loose particle shape. As corrosion time increases from 2 days to 8 days, corrosion layer thickness increases from about 15 to 24 μm for sample 1.     

Die Korrosion des Bleis in tetrafluoborsauren Elektrolytlösungen

The corrosion of lead in acid tetrafluoborate electrolytes The corrosion of 99,985% lead in acid tetrafluoborate electrolytes, predominantly 1 mole/litre HBF₄ and 2 mole/litre Pb (BF₄)₂, was investigated. The corrosion rate in air saturated solution at 20°C is 35 μA/cm², which corresponds to 1 mm/a. Oxygen corrosion predominates (corrosion is rather reduced under argon). At higher temperatures, corrosion rate increases by an order of magnitude, and acid corrosion has a greater share due to a decrease of hydrogen overvoltage on lead and solubility of oxygen. Cementable additives like Cu⁺⁺, Sb⁺⁺⁺ and Pd⁺⁺ are found to enhance the initial corrosion rate by up to two orders of magnitude. However, after 10–20 hours, the original value is reestablished. Bi⁺⁺⁺ is cemented as well; the resulting acceleration of corrosion is proportional to the additive concentration and decreases but slowly. Oxidants like Fe⁺⁺⁺ or quinone accelerate the dissolution of lead as well and are consumed stoichometrically. Reducing agents like Fe⁺⁺, V⁺⁺⁺ or hydroquinone are not able to act as a mediator for air corrosion. Nitrate ions are virtually inert in the given concentration range. Consequences in reference to the lead dissolution secondary battery are discussed. Self discharge in the absence of O₂ is very low. On the other hand, it is possible by oxygen corrosion to redissolve lead, which has accumulated on the electrode. In this way, the battery can be brought back to its original state.     

Enhanced corrosion behavior and mechanical properties of AZ91 magnesium alloy developed by ultrasonic-assisted friction stir processing

In this study, ultrasonic-assisted friction stir processing (UaFSP) and friction stir processing (FSP) were conducted on AZ91 magnesium alloy sheets, and their microstructure, corrosion behavior, and mechanical properties were comparatively investigated. Scanning electron microscopy, open-circuit potential, and potentiodynamic polarization were used to study the corrosion behavior of the material. Electrochemical measurements reveal that employing UaFSP, the corrosion rate of the AZ91 magnesium alloy was significantly reduced where lower corrosion current density for UaFSP specimens was obtained (2.09 µA/cm²) compared with 3.42 µA/cm² for the FSP and 6.82 µA/cm² for the base metal. This is mainly attributed to the alteration of morphology and better distribution of the β-Mg₁₇Al₁₂ phase during UaFSP. By using ultrasonic vibration in FSP, a finer grain structure was obtained, which improved the tensile strength and hardness of the AZ91 Mg alloy.     

The influence of ion implantation on the corrosion behaviour of iron in acid solution

The influence of ion implantation on the aqueous corrosion of pure iron in IN H₂SO₄ was studied. The iron was bombarded with 5 × 10¹⁵–10¹⁷ ions.cm^?2 of Ne, Ar, Cu, Pb and Au. The current density-potential curves of the implanted samples were measured and compared with that of untreated pure iron. Ne⁺ and Cu⁺ bombardments lead to a slightly higher corrosion rate in comparison with untreated iron. Pb⁺ depressed the corrosion rate by orders of magnitude, Au⁺ enhanced it by a factor of more than ten. The effect is attributed to a reduction or an increase of the activity of the electrode surface with respect to the cathodic hydrogen evolution reaction, i.e. the ion implantation influences strongly the exchange current density of the hydrogen evolution reaction. A marked influence of the implantation on the anodic behaviour of the corroding metal could also be observed.     

Direct electrosynthesis of polyaniline–montmorrilonite nanocomposite coatings on aluminum alloy 3004 and their corrosion protection performance

Homogeneous and adherent polyaniline–montmorrilonite (MMT) nanocomposite coatings were electrosynthesized on aluminum (Al) alloy 3004 (AA 3004) by using the galvanostatic polarization method. The synthesized coatings were characterized by UV–Vis absorption spectrometry, Fourier transform infrared spectroscopy, X-ray diffraction patterns and scanning electron microscopy. The corrosion protection effect of the coatings was demonstrated by performing a series of electrochemical experiments of potentiodynamic and impedance measurements on Al in 3.5 wt% aqueous NaCl electrolytes. The corrosion current (i_corr) values decreased from 6.55 μA cm⁻² for uncoated Al to 0.102 μA cm⁻² for nanocomposite-coated Al under optimal conditions.     

Microstructure,microhardness and corrosion resistance of laser cladding Ni–WC coating on AlSi5Cu1Mg alloy

The microstructure, microhardness, and corrosion resistance of laser cladding Ni–WC coating on the surface of AlSi5Cu1Mg alloy were investigated by scanning electron microscopy, X-ray diffraction, microhardness testing, immersion corrosion testing, and electrochemical measurement. The results show that a smooth coating containing NiAl, Ni₃Al, M₇C₃, M₂₃C₆ phases (M=Ni, Al, Cr, W, Fe) and WC particles is prepared by laser cladding. Under a laser scanning speed of 120 mm/min, the microhardness of the cladding coating is 9–11 times that of AlSi5Cu1Mg, due to the synergistic effect of excellent metallurgical bond and newly formed carbides. The Ni–WC coating shows higher corrosion potential (−318.09 mV) and lower corrosion current density (12.33 μA/cm²) compared with the matrix. The crack-free, dense cladding coating obviously inhibits the penetration of Cl⁻ and H⁺, leading to the remarkedly improved corrosion resistance of cladding coating.     

Effects of copper on the corrosion properties of low-alloy steel in an acid-chloride environment

The influence of Cu addition on the corrosion resistance of low-alloy steel in an acid-chloride solution was investigated by electrochemical methods, such as potentiodynamic polarization tests and an electrochemical impedance spectroscopy (EIS). The XPS analysis of the corroded surfaces indicated the formation of protective Cu₂O and Cu(OH)₂ layers on the surface. The formation of Cu products on the surface reduced the uniform corrosion rate of the steel, but promoted localized corrosion due to the galvanic interaction between the covered areas of copper oxide/hydroxide and the uncovered areas on the surface of steel.     

Characterization and corrosion studies of fluoride conversion coating on degradable Mg implants

Fluoride conversion coating was synthesized on magnesium (Mg) by immersion treatment in hydrofluoric acid (HF) at room temperature, with the aim of improving the corrosion resistance of Mg in applications as degradable implant material. After an immersion period of 24 h in 48% HF, the samples carried a bronze color, and the conversion coating was dense and free of cracks. Field-emission scanning-electron microscopy (FE-SEM) of the cross-section revealed a coating thickness of about 1.5 μm. Atomic-force microscopy (AFM) recorded an average surface roughness of ∼ 21 nm for the coated sample, similar to that of the untreated one (∼ 17 nm). The coating was mainly composed of magnesium fluoride (MgF₂) as identified by thin-film X-ray diffractometry (TF-XRD), consistent with compositional analysis using X-ray photoelectron spectroscopy (XPS). The MgF₂ was in the form of crystallites of a few nm. A small amount of oxygen was present inside the coating, suggesting that some F⁻ ions are replaced by hydroxyl (OH⁻) ions in the MgF₂ structure, or that a small amount of Mg(OH)₂ was present. The corrosion resistance of untreated and conversion coated Mg in Hanks' solution was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests, and immersion tests. EIS results showed a polarization resistance of 0.18 kΩ cm² for the untreated Mg and 5.2 kΩ cm² for the coated sample, giving an improvement of about 30 times. Polarization tests also recorded a reduction in corrosion current density from 400 μA/cm² to 10 μA/cm², showing an improvement of about 40 times. The galvanic effect between untreated and fluoride-coated Mg samples was small. Immersion tests in Hanks' solution also resulted in a much milder and more uniform corrosion damage on the fluoride-coated samples. The results of the present study showed that fluoride coating by conversion treatment is a simple and promising way of enhancing the corrosion resistance of Mg in Hanks' solution, or that it may be employed as a pretreatment step for subsequent coating.     

Corrosion of structural constituents of 2017 aluminium alloy in acidic solutions containing inhibitors

The objective of this study is to establish the corrosion behaviour of the most important structural constituents of the aluminium alloy 2017 in orthophosphoric acid solutions containing heteropolyoxomolybdate, tungstate and vanadate. These are potential candidates for replacing toxic hexavalent chromium species in stripping solution for anodic coatings. The corrosion rate of the alloy is estimated with linear polarisation method. It decreases from 0.58 mA cm⁻² in uninhibited solution to 0.10 mA cm⁻² in a solution containing heteropolyoxomolybdate species. Microscopic studies reveal that heteropolyoxomolybdate species inhibit corrosion of the matrix and intermetallic Al₁₅(Fe,Mn)₃(Si,Cu)₂ but not Mg₂Si. Intermetallic Al₂Cu remains not corroded. Heteropolyoxotungstate species virtually do not inhibit the corrosion of the alloy. The solution containing vanadium species is not stable with time and the corrosion rate is not determined. Nevertheless, corrosion of the matrix is inhibited, but intermetallics Al₁₅(Fe,Mn)₃(Si,Cu)₂ together with Mg₂Si are dissolved. X-ray photoelectron spectroscopy is used for examination of a corrosion product precipitated on the surface.     

Corrosion behavior of porous Ti3SiC2 in nitric acid and aqua regia

Porous Ti₃SiC₂ with high purity was synthesized using TiH₂, Si and C powders with mole ratio of Ti to Si to C being 3:1.2:2 by reactive synthesis method. The corrosion behaviors of porous Ti₃SiC₂ in nitric acid and aqua regia were investigated by immersing test. Scanning electron microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology, compositions and element contents of the samples before and after corrosion to determine the corrosion product and corrosion mechanism. The mass loss values of porous Ti₃SiC₂ are 26.9 and 132.5 μg/cm², respectively after immersing in nitric acid and aqua regia for 600 h. The results indicate that Ti₃SiC₂ transforms to Ti₅Si₃ which has better corrosion resistance in nitric acid and aqua regia with mass loss values of 9.34 and 7.06 μg/cm² under the same immersing time, respectively. The dramatic dissolution of porous Ti₃SiC₂ in the acids is due to its special microstructure.     

Korrosion des Hastelloy C 4 und anderer metallischer Werkstoffe in heißen,konzentrierten Salzlaugen

Corrosion of Hastelloy C4 and different metallic materials in hot concentrated salt brines In a quaternary salt brine saturated at 55°C with magnesium chloride, potassium chloride and sodium chloride, polarization curves were measured in the temperature range from 100°C to 200°C at different materials in order to study their corrosion behaviour. Steels and nickel corrode in the active state. The corrosion current density of an unalloyed steel at 100°C was about 20 μA/cm² corresponding to a removal rate of 0.2 mm/a. Iron-silicon and nickel corrode significantly slower at a rate of a few μA/cm². Steady state corrosion rates of Hastelloy C 4 and of titanium at 100°C are 10 nA/cm² and less than 4.5 nA/cm², respectively. For both materials, the susceptibility to pitting grows with the temperature and with the chloride concentration. The steady state corrosion rates of passive Hastelloy C 4 depend on temperature according to an activation enthalpy of 85 kJ/mol and become about 5 μA/cm² at 200°C. Even at high temperatures steady states are attained rather slowly within about one day. The critical pitting potentials approach the corrosion potentials in deaerated solution at a rate of about 0.8 mV/K. At 200°C the critical pitting potential is only 90 mV positive to the corrosion potential. Thus, Hastelloy C 4 may be used at high temperatures, only if it is cathodically protected.     

The Influence of Electrophoretic Potential on Ni—Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-Composite Coating

In this study, the effect of electrophoretic voltage changes on Ni—Al₂O₃ nano-composite coating via two step process electrophoretic, and electrochemically on 1100 Al substrate on morphology, corrosion and wear behaviour were studied. In the first step of deposition for determining the optimum amount of Teri Ethanol Amin activator in electrophoretic suspension Transmission Electron Microscopy (TEM) was used. The amount of alumina particles, Nickel ions in the coating and morphology were studied by Energy-dispersive X-ray spectroscopy (EDX) and Field-Emission Electron Microscopy (FESEM). Nanoparticles distribute more homogenous in deposit within using 40 V voltage. Corrosion behaviour of coating was investigated by polarization technique in 3.5 wt % NaCl which shows a decrease in corrosion current from 13.7 μA/cm² to 1.46 μA/cm² versus bare sample.     

Self-healing mechanism of a protective film prepared on a Ce(NO3)3-pretreated zinc electrode by modification with Zn(NO3)2 and Na3PO4

Self-healing mechanism of a protective film against corrosion of zinc at scratches in an aerated 0.5 M NaCl solution was investigated by polarization measurements, X-ray photoelectron spectroscopy (XPS) and electron-probe microanalysis (EPMA). The film was prepared on a zinc electrode by treatment in a Ce(NO₃)₃ solution and addition of aqueous solutions containing 9.98 or 19.9 μg/cm² of Zn(NO₃)₂ · 6H₂O and 55.2 μg/cm² of Na₃PO₄ · 12H₂O. After the coated electrode was scratched with a knife-edge crosswise and immersed in the NaCl solution for many hours, polarization measurements, observation of pit formation at the scratches, XPS and EPMA were carried out. This film was remarkably protective and self-healing against zinc corrosion on the scratched electrode. The cathodic and anodic processes of zinc corrosion were markedly suppressed by coverage of the surface except for scratches with a thin Ce₂O₃ layer containing a small amount of Ce⁴⁺ and the surface of scratches with a layer composed of Zn₃(PO₄)₂ · 4H₂O, Zn(OH)₂ and ZnO mostly.