Effect of antimony additions on the microstructure and performance of Zn–Mg–Al alloy coatings

Individual and combined additions of calcium and antimony on microstructure and mechanical properties of squeeze-cast AZ91D magnesium alloy

Effect of Antimony and Yttrium Addition on the High Temperature Properties of AZ91 Magnesium Alloy

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

The corrosion behavior on commercial stainless steel SS 304 in Nano fluids water-Al2O3 system at pH 3 until 7 conditions has been investigated using electrochemical methods. The electrochemical tests were performed with and without the addition chlor to adjust of pH Nano fluid condition. The pH of nano fluid for testing corrosion stainless steel 304 are 3.18,.3.65, and 5. 9. The electrochemical technique used in this study, were open circuit potential (OCP), galvanodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of open circuit potential tests showed that the corrosion potential (Ecorr) values of stainless steel 304 in nanofluid at three pH values are slightly different between pH neutral and acidic. At pH 5.9 corrosion potential more positive compare with at acid pH 3.18. The positive potential of corrosion potential at pH 5.9 due to development of chromium oxide (Cr2O3) film formed on stainless steel is more stable in 5.9 than in acidic with the presence of Cl. However, galvanodynamic polarization of stainless steel SS 304 in nanofluid showed that the lowest corrosion of stainless steel SS 304 in nanofluid at pH 5.9 than stainless steel at condition in acidic pH 3.18 and 3.65. EIS study shows that stainless steel SS 304 in nanofluid showed the higher impedance at higher pH than at in acidic condition at lower pH. The higher impedance indicated that the passive film of Cr2O3 formed on the surface of stainless steel and reduce corrosion rate. In terms of corrosion rate values, stainless steel alloy showed the best corrosion rate in low pH nanofluid compared with high pH value. This shows that the interaction between Nano fluids and the stainless steel have no significant effect onto its corrosion behavior.

In vitro bioactivity and biocompatibility of magnesium implants coated with poly(methyl methacrylate) - bioactive glass composite

<div class="htmlview paragraph">Internal corrosion in mufflers caused primarily by exhaust condensate, is known to have a major impact on their durability. UOP's novel technology for reducing the corrosiveness of exhaust system condensate employs a small amount of unique zeolite adsorbent which, when the car engine is shut down, adsorbs the water and acid precursors from the gas phase in the interior of the muffler before they can condense and attack the mufflers internal parts. Vehicles exhaust gas desorbs the water and acid precursors while the engine is in operation, preparing the adsorbent for the next engine shutdown.</div> <div class="htmlview paragraph">Data is presented from a series of 5 statistically designed vehicle fleet tests which demonstrate that the corrosion rates of actual muffler parts can be reduced by more than 65%, when zeolite adsorbents are inserted in the muffler. Both ASTM Gl type corrosion coupons and micrographic examination of muffler parts show the dramatic reduction in corrosion rates experience with zeolite equipped mufflers as compared to control populations from the fleet tests.</div> <div class="htmlview paragraph">This proven technology enhances muffler service life with all types of corrosion resistant steels. A mathematical model for muffler service life that employs actual measured corrosion rates for various corrosion resistant steels, shows that a reduction in internal corrosion rate of 50%. due to the use of zeolite can actually increase service life of a muffler by up to 28%. In salt belt locations and up to 51% in sun belt areas.</div> <div class="htmlview paragraph">The paper includes a discussion of the adsorption processes occurring inside the muffler, and their effect on the amount and pH of the exhaust condensate.</div>

One aspect of effective steam/water cycle chemical treatment programs is their ability minimize corrosion and corrosion related failures. In this study, we examine how corrosion product layers on the surface of tubing samples impact corrosion rate for a series of test specimens prepared from boiler/steam piping provided from operating power plants. Corrosion rates were estimated using the following electrochemical techniques: linear sweep voltammetry (LSV), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Two sources of Tafel slopes were the standard assumptions used if the corrosion mechanism is not known and those obtained from LSV curves. In total, five variations of corrosion rate measurements were compared. For these corrosion tests, water chemistries representative of conditions that induced online hydrogen damage and offline pitting were used. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS/EDX) were the electron microscopy techniques applied to examine the corrosion product layers. Using these techniques, the microstructure and elemental composition of the tubing sample corrosion product layers were examined. These techniques could be utilized to evaluate the effectiveness or reduction in corrosion rates with the application of film forming products.

Cracking of reinforced concrete can result in substantial reduction in service life owing to rapid initiation of steel corrosion. Supplementary cementitious materials (SCMs) can alter not only the pore solution chemistry but also the environment surrounding the steel and lead to significant reductions in corrosion rate. The impact of binder type on corrosion rate was assessed using seven concrete mixtures comprising ordinary Portland cement (PC) and blends of PC with ground granulated blast-furnace slag, fly ash, condensed silica fume and a ternary blend. Corrosion rates were measured in prismatic specimens with crack widths of 0·2 mm or 0·7 mm. For 20 mm cover, all the SCMs resulted in at least a 50% reduction in corrosion rate compared with the PC control. Increase in crack width from 0·2 mm to 0·7 mm increased corrosion rate in all cases, but had far less impact than that of the SCMs. Increase in cover depth from 20 mm to 40 mm had substantial benefits for PC specimens, reducing corrosion rates by more than half; the same benefits were not observed in specimens using SCMs. This was ascribed to corrosion rates of SCM concretes being controlled primarily by resistivity of the system, while rates in PC specimens were controlled mainly by oxygen availability and thus cover depth.

The paper presents the effect of vanadium addition to aluminum and aluminum grain refined by titanium on the micron level, in the range from 0.005 wt % to 0.236 wt %, on their corrosion resistance in acidic solution, HCl, at three different temperatures namely: 25 °C, 40 °C and 60 °C. It was found that the corrosion rate was slightly increased by the addition of any percentage of vanadium at 25 °C. Furthermore, it was found that the corrosion rate increased with the increase of temperature at any percentage of vanadium addition in the case of both aluminum and aluminum grain refined by titanium. However it was found that addition of vanadium at any percentage to either aluminum or aluminum+ titanium, resulted in decrease of the corrosion rate i.e. improvement in their corrosion resistance in acidic solution at 40 °C and 60 °C. The maximum achieved reduction in corrosion rate was 77 % at 40 °C and 0.148 wt % vanadium addition.

<div class="htmlview paragraph">Cast aluminum alloys 356 and 319 and wrought alloy 3003 were corrosion tested in a commercial (Fleetguard DCA-4) supplemental coolant additive (SCA) package modified by varying the potassium nitrate level.</div> <div class="htmlview paragraph">Electrochemical techniques were used to determine the stability of the passive film as a function of nitrate concentration. Cyclic potentiodynamic polarization and cyclic galvanostaircase polarization were the principle techniques used and compared. In the presence of the other inhibitors, the passive film stability did not change as the nitrate concentration varied. The corrosion resistance of each alloy was more dependent on the alloy chemistry with 3003 being the most resistant and 319 being the least. The two electrochemical techniques provided results consistent with each other.</div> <div class="htmlview paragraph">With the introduction of advanced materials and processes to the heavy duty diesel engine, the challenge in formulating a coolant is to provide adequate protection for all the materials in the cooling system. Cast and wrought aluminum alloys are increasingly being used or are being considered for use in such components as manifolds, pump housings, and radiators. In the past, silicates have been used in coolants to provide protection to aluminum alloys, however overconcentration of the SCA has lead to silicate dropout in the form of a gel which interferes with coolant flow and heat transfer. The use of a low silicate phosphate/molybdate based additive package is an improvement over the traditional borate/nitrite system, however it still contains substantial amounts of nitrate. Although nitrate is added to improve pitting protection in aluminum, excessive amounts can promote brass cracking.</div> <div class="htmlview paragraph">Gravimetric techniques such as the ASTM D-1384 glassware test, cavitation, and hot surface testing have traditionally been used to develop SCA formulations for heavy duty use. Although electrochemical testing has been used extensively in diverse applications such as nuclear power generation, petrochemical production and industrial coatings development, it has only relatively recently come to be accepted for characterizing material behavior in heavy duty, cooling systems (<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span> and <span class="xref">5</span>). In addition to the shorter test times for determining an “instantaneous” corrosion rate, valuable information can be obtained as to an alloy's natural passivity and the effectiveness of inhibitors in forming protective films (<span class="xref">6</span>). A brief summary of electrochemical testing theory is given in the Appendix and a list of terms and symbols are defined after the Conclusion section.</div> <div class="htmlview paragraph">The purpose of this study is to apply electrochemical corrosion measurement techniques to evaluate the effect of nitrate concentration in Fleetguard's DCA-4 on several typical aluminum alloys, both cast and wrought. It is hoped that the results of this will allow us to specify the minimum amount of nitrate for adequate pitting protection for these alloys. Cyclic potentiodynamic polarization and cyclic galvanostaircase polarization were the primary experimental techniques used to study passivation as a function of nitrate concentration. Potentiodynamic polarization (Tafel plots) were used to measure corrosion current, and hence, rate and polarization resistance. While cyclic potentiodynamic polarization is more commonly used to study repassivation, the kinetic effects on aluminum alloys in particular make the results from this technique dependent on the parameters chosen in making the scan. The pitting potential and the protection potential are dependent, for example on scan rate. To avoid these problems, Hirozawa has proposed the use of the cyclic galvanostaircase technique. This method and its advantages are described in more detail elsewhere (<span class="xref">7</span>, <span class="xref">8</span> and <span class="xref">9</span>). In this study, these two methods will be compared in our specific environment.</div>

The paper presents the effect of vanadium addition to aluminum grain refined by titanium, in the range from 0.005 wt % to 0.236 wt %, on corrosion rate of these micro alloys in caustic soda (NaOH) solution at different temperatures. The corrosion rate decreased by the addition of any percent of vanadium at 25°C compared to pure Al. The corrosion rate increased with increase of solution temperature from 25 to 40 and 60 °C at any percent of vanadium addition. However, addition of vanadium reduced the corrosion rate at these temperatures at most wt.% of V addition. The maximum achieved reduction in corrosion rate due to vanadium addition was 40 % at 0.148 wt % and 60°C. The addition of 3 % potassium dichromate as corrosion inhibitor to NaOH solution reduced the average corrosion rates at any wt.% of vanadium. The inhibition efficiency ranged from 44- 58% at 25 °C and from 97-99% at 40 and 60°C.

Plasma sprayed graphene reinforced titanium nitride composite coating: An effective solution for mitigating the corrosion attack

Aged oil pipeline production systems, historically designed without corrosion protection due to predominantly oil-wetted conditions, now face significant changes as increased water content in produced oil arises from field maturation. This work investigates the corrosion inhibition properties of sweet crude oil on carbon steel 1018 in a CO2-saturated NaCl solution using electrochemical testing (open circuit potential, polarization resistance, electrochemical impedance, potentiodynamic polarization) and surface characterization (SEM, EDS) techniques at 50 °C and pH 6. Carbon steel specimens were immersed in crude oil for durations ranging from 0 to 144 h before undergoing corrosion testing. Results showed that a 144-h immersion in crude oil led to an 88 % reduction in corrosion rate, comparable to the efficiency of standard quaternary ammonium-based inhibitors. Furthermore, a semi-empirical model predicting uniform CO2 corrosion rates for varying oil immersion durations is proposed and validated by comparing its predictions with experimental data from the electrochemical tests.

Reinforced concrete repairs in beams

Influences of aggressive ions in human plasma on the corrosion behavior of AZ80 magnesium alloy