Chloride Alloy Research Articles

Electrochemical and spectroscopic study on corrosion behavior of Ni-based alloys in chloride melts: Materials for an integral molten salt fast reactor

For the long-term operation of integral molten salt fast reactor safety, it is necessary to select structural materials with high corrosion resistance such as Ni-based alloys in high-temperature chlorides of specific composition. In this study, the corrosion behavior of Inconel 600, Inconel X750, Hastelloy C-276, and Incoloy 800, which are the candidates for the structural materials in NaCl-KCl-MgCl2 melt at 723 K and NaCl-CaCl2 melt with CeCl3 or LaCl3 at 873 K were investigated by electrochemical and spectroscopic analyses toward designing materials used in the integral molten salt fast reactor. The corrosion rates were estimated based on the elemental analysis of alloy surfaces by glow-discharge optical emission spectroscopy and the corrosion current density by linear polarization technique. It was found that the trend of corrosion rate for each alloy changed significantly depending on the composition of the chloride melts. The electrochemical behavior obtained from the linear polarization measurement and the impedance spectroscopy indicated that the cathodic reaction during the corrosion process was different among each melt. To discuss the effect of molten salt composition on corrosion behavior, the melt structure was investigated by high-temperature Raman spectroscopy and density functional theory calculation. The results indicated that the coordination structure of oxide ions, which are corrosion products formed in the cathodic reaction, changed depending on the composition of the chloride melts. The reported data show that it is important to control the corrosion process by clarifying the structure of each melt in order to select a highly compatible system of molten salt and structural material.

Insitu electrochemical impedance spectroscopy of PT-7 M and Fe-Ni-Cr alloys in chloride containing ammonia medium at high temperatures

Corrosion of Titanium-based PT-7 M and Fe-Ni-Cr-alloy was investigated in chloride-containing ammonia at 288 °C at pH288 °C7.23 and pH288 °C7.75. Oxide on Fe-Ni-Cr-alloy was compact compared to PT-7 M. EIS at 288 °C indicated lower metal loss for Fe-Ni-Cr -alloy. At lower pH, Fe-Ni-Cr exhibited an incubation period that is attributed to the adsorption of Cr-species. At lower pH, the metal loss was linear for PT-7 M, but repassivation occurred at higher pH. Pitting was not observed and the point defect-densities decreased at higher pH for both supporting a lower metal loss. Corrosion resistance of Fe-Ni-Cr-alloy matched that of the PT-7 M under the given conditions.

Anodic selective dissolution of copper alloys in chloride and carbonate melts

The synthesis of materials with a developed electrode surface of the electropositive component of the alloy and a significant near-surface layer was performed by anodic selective dissolution of copper alloys (Cu63–Zn37, Cu40–Zn37, Cu65–Ni35, Cu35–Ni65 and Cu50–Al50). The morphological and electrochemical characteristics of the obtained electrode materials based on mesoporous copper demonstrate its prospects for catalysis substrate application, electrodeposition of materials with specified parameters, and for the low-wear anode base formation.The media was combination of lithium, sodium, potassium carbonates (30 : 30: 40 mol. %), as well as low-melting eutectic mixtures of alkali metal chlorides of various compositions (especially CsCl–KCl–LiCl (54.4 : 15.3: 30.3 wt %) in the temperature range of 623–923 K. The object of the study was copper alloys such as copper-zinc, copper-aluminum, copper-nickel. Anodic selective dissolution was performed under the following electrolysis modes: galvanostatic and potentiostatic modes; rectangular polarization; cyclic voltammetry.The values of geometric current densities were 100, 200, 300, 900, 1400 A/m2. The applied anode potential was +0.1, +0.2 and + 0.5 V (from the open circuit potential of the material). The platinum reference electrode was used. The resulting surface structures were investigated using micro- and X-ray phase analysis. The composition of frozen melt samples after electrolysis completion was studied by atomic absorption analysis. The resulting surface structures were investigated using micro- and X-ray phase analysis.The influence of the following factors on the surface structure of the final anode product was studied and discussed: composition of the studied alloy (the amount of electronegative component in the alloy, as well as its nature); electrolyte composition (chloride and carbonate melt); temperature of selective dissolution (350, 500 and 650°С)It was shown that it is possible to change the nature of the binary alloy dissolution by changing the kinetic parameters (electrolyte composition, temperature), and to obtain a mesoporous material with a developed surface, suitable for heterogeneous catalysis, structural design of electrochemical and electrical devices.a) the most perspective copper-based alloy for the formation of nanoporous and mesoporous materials in salt melts is brass Cu63–Zn37;b) the smallest average pore size had samples of brass Cu63–Zn37 in experiments with chloride melt; in galvanostatic mode the pore size was 500 nm (under given conditions – 200 A/m2, 350 °C); in potentiostatic mode – 250 nm (+0.1 V, 500 °C). With the temperature decreasing it is possible to reduce this indicator by 1.5–3.0 times;c) the square-wave potentiometry method was used to form a developed near-surface layer in several stages;g) cyclic voltammetric curves were obtained, which can be used to prognosticate and describe the stages of the anode process;e) the potentials of open circuits were obtained for the studied samples;g) by dissolution of copper-aluminum alloy in galvanostatic mode was formed the nanofiber on the surface with thread size less than 20 nm.2. The influence of the temperature, the nature of the second component of the alloy and the salt electrolyte (chloride) on the formation of the developed surface layer of the alloys under study was established:a) the increase in temperature leads to a decrease in the development of the surface layer;b) copper-nickel samples are depleting by copper due to the fact that copper is an electronegative component of the alloy in chloride melts, while the formation of developed surface layer enriched with nickel takes place;c) the increase in the content of the electronegative component leads to a decrease in the development of the surface.It was shown that it is possible to change the nature of the binary alloy dissolution by changing the kinetic parameters (electrolyte composition, temperature), and to obtain a mesoporous material with a developed surface, suitable for heterogeneous catalysis, structural design of electrochemical and electrical devices.

Environmentally assisted cracking behavior of U-bend specimens of Mg–RE alloys in chloride containing basic solution

Abstract Environmentally assisted cracking (EAC) behavior of two Mg-rare earth (RE) alloys such as Mg–Zn–Gd–Nd–Zr (EV31A) and Mg–Y–Nd (WE43C) alloys was investigated by using U-bend specimens. Open circuit potentials (OCP) of the U-bend specimens were monitored during the EAC tests in 0.1 M NaOH solution with different chloride concentrations at room temperature. EV31A (as-received, and peak aged) and WE43C (peak aged) specimens failed by SCC in 80 ppm chloride containing 0.1 M NaOH solution at OCP. When the EAC initiation occurred, the OCP decreased continuously. Irregular fluctuations of the OCP were observed in the absence of EAC. The OCP versus time profile could be used for monitoring EAC failure of the Mg–RE alloy components in real life service. Applied potentials did not cause cracking of the EV31A alloy in 80 ppm Cl− containing 0.1 M NaOH. Accelerated cracking was observed on the WE43C alloy in peak-aged condition under the applied potentials in the transpassive region when compared to that of OCP condition. Overaging decreased the susceptibility to cracking.

Effect of Temperature on Corrosion behavior of Copper Silver Phosphorus Brazing Alloys in Chloride Containing Solution

The groups of phosphorus-containing brazing alloys are the most favored filler metals used for joining copper and copper-base alloys. These brazing alloys are expected to have the optimum corrosion resistance during the application. However, failures arise at the braze joint generally caused and initiated by the corrosion of the brazing alloys when used at higher temperature than the room temperature. Since most studies of the phosphorus containing brazing alloys were performed at room temperature, this work has been extended to investigate the effect of various temperature on the corrosion behavior. Electrochemical measurements were carried out to observed the temperature effect with the temperature variation of 25, 40, 55 and 70 °C in 3.5% NaCl electrolyte. As the results, the copper-silver-phosphorus brazing alloy was undergone a selective dissolution by the attack of Cl-to the copper element. The temperature dependence of the alloy showed in agreement with the relationship of 2.3RT/F that have similar manner on pure copper tafel region. The schematic diagrams of the corrosion process were then proposed. This work could be helpful to understand in the field practically because the application temperature is usually higher than that of room temperature in general.

Hot corrosion of different alloys in chloride and carbonate molten-salt mixtures under argon atmosphere

Molten eutectic salt mixtures can be used as thermal energy storage materials or heat transfer fluids at concentrated solar power plants. The targeted operating temperature for the next generation concentrated solar power plants is 700 °C. Although chloride and carbonate eutectic salt mixtures with high thermally stable temperatures were reported to have great thermophysical properties, their corrosion to alloys at high temperature has not been thoroughly studied. Corrosion of the thermal energy storage materials and heat transfer fluids to alloys is critical, and oxygen in air is confirmed to accelerate the corrosion significantly. In the present study, three eutectic mixtures of NaCl-KCl-ZnCl2, Li2CO3-Na2CO3-K2CO3 and LiF-Na2CO3-K2CO3 were considered as high temperature thermal energy storage materials or heat transfer fluids. Corrosion of stainless steel 316, Hastelloy C276, Inconel 625 and 718 immersed in the three salt mixtures up to 21 days were experimentally investigated at 700 °C under argon atmosphere. The specimens after corrosion tests were characterized by scanning electron microscope, energy dispersive spectroscopy and X-ray diffraction. The results show that SS316 is only compatible with the LiNaK carbonate-salt and the corresponding corrosion rate is lower than 95 μm/year. Both C276 and In625 have relatively good corrosion resistance for the NaKZn chloride-salt and LiF-NaK carbonate-salt, and the corrosion rates are lower than 78 μm/year. The highest corrosion rate over 1700 μm/year is detected for In625 immersed in the LiNaK carbonate-salt. In addition, In718 shows excellent corrosion resistance less than 10 μm/year immersed in all the three salt mixtures.

Newly-Developed Molybdate-Based Protective Coatings for AZ31D Magnesium Alloys

Molybdate-based eco-friendly protective coatings were developed for AZ31D magnesium alloy. Mg AZ31D substrates treated first in boiling molybdate for oxide thickening pretreatment followed by molybdate chemical conversion coating. Highly protective and uniformly distributed molybdate coatings were deposited over Mg AZ31D substrates. The corrosion resistance enhanced from ~ 2 KΩ.cm2 for the as-polished samples to ~ 8 KΩ.cm2 for the samples treated under the boiling molybdate conditions. The high performance of molybdate-based coatings can be attributed to molybdenum oxide role in rejecting chloride ions. It also stimulates blocking the pits and cracks initiated at the surface under the effect of corrosive medium attack. The designed coating treatment is characterized by its simplicity in which it can be deposited over the Mg AZ31D surface at room temperature via a free immersion technique. The eco-friendly coatings seems very promising and effective for improving the corrosion resistance of magnesium alloys in chloride containing solutions. Subsequent organic top coats are needed for adequate corrosion protection performance. The newly-developed approach can be extended to include other boiling solutions for oxide thickening as well as other metal substrates to explore its universal application.

Corrosion resistant coatings based on synergistic effects of alkaline etching and molybdate treatment for AZ31D magnesium alloy

ABSTRACTEco-friendly, non-toxic protective coatings deposited from molybdate–based solutions have been developed as undercoat thin-films (for subsequent organic top coats) for AZ31D magnesium alloy. Direct treatment of Mg AZ31D substrates with molybdate–based solutions has no significant effect on the overall surface resistance (charge transfer resistance). Alkaline etching of Mg AZ31D surfaces using KOH solution prior to molybdate conversion coating showed significant enhancement in the corrosion resistances The optimum conditions of alkaline etching and molybdate treatment steps have been determined. The total surface resistance was improved from 2.1 × 103 Ω.cm2 (for as-polished AZ31D) to be 3.2 × 103 Ω.cm2 for the alkaline etched samples followed by 10 g L−1 molybdate treatment. The resistance to localised corrosion (pitting and crevice) improved significantly after applying the alkaline etching step. Molybdate–based coatings formed on Mg AZ31D exhibited a network of flower-like and needle-like protective molybdenum oxide structures which are belived to be responsible for the improvement in the pitting and crevice corrosion resistance. They impede the corrosive media from reaching the bare metal and hence improve the pitting and crevice corrosion resistances. This simple eco-friendly, low-toxicity pretreatment approach seems very promising and effective for improving the corrosion resistance of magnesium alloys in chloride containing solutions.

Pitting Corrosion Behavior of 304 SS and 316 SS Alloys in Aqueous Chloride and Bromide Solutions

The importance of the present work falls on the pitting corrosion behavior investigation of 304 SS and 316 SS alloys in 3.5 wt% of aqueous solution bearing with chloride and bromide anion at different solutions temperature range starting from (20-50)oC due to the pitting corrosion tremendous effect on the economic, safety and materials loss due to leakage. The impact of solution temperatures on the pitting corrosion resistance at 3.5wt% (NaCl and NaBr) solutions for the 304 SS and 316 SS has been investigated utilizing the cyclic polarization techniques at the potential range -400 to1000 mV vs. SCE at 40 mV/sec scan rate followed by the surface characterization employing Scanning Electron Microscope. The results show that a significant decline in the pitting corrosion potential Ep values of both stainless steel alloys in chloride and bromide solution during temperature increase attributed to the pitting corrosion potential decreased arises from the modification of the passive film properties. The surface examination using optical microscope and scanning electron microscope prove the occurring of higher pitting density over 304 SS in chloride solution than that observed in bromide solution with a non-circular lacy cover pitfall out at the center and falls inside the pits hall in comparison to the isolated circular lacy cover pit formed on 316 SS in 3.5wt% NaBr solution at 50 oC.

Synergistic effects of alloying elements in Cu-ternary alloys in chloride solutions

Copper alloys are important materials for many industrial applications. The addition of Al, Ni and Zn to Cu either as single alloying element in binary alloys like brasses and bronzes or the well-known Cu-Ni alloys or as couples in ternary alloys leads to specific properties important for different applications. In this paper we are interested to investigate the effect of the presence two alloying elements with copper and to investigate the electrochemical behavior of these alloys in chloride containing solutions. It is important to compare the corrosion behavior and the stability of each alloy in these media. For this reason we have used Cu-10Al-10Ni, Cu-10Al-10Zn and Cu-10Ni-10Zn, in which the ratio of Cu is kept constant and the two alloying elements of equal percentage. All investigations were carried out in stagnant naturally aerated neutral 3.5 mass to volume % NaCl solutions. Different electrochemical techniques and electrochemical impedance spectroscopy, EIS, were used. It was found that the Cu-10Al-10Zn alloy is more stable than both the Cu–10Al-10Ni and Cu-10Al-10Zn alloys in this chloride solution. EIS measurements have shown that a thicker and more resistive passive film is formed on the Cu-10Ni-10Zn alloy surface. The formation of such passive film was discussed and the different alloy surfaces examined by scanning electron microscopy and subjected to EDAX analysis. The surface analysis has shown the participation of the different alloying elements in the passive film according to the alloy constituents and also that the chloride ions are deeply penetrated in the alloy.

HOT CORROSION BEHAVIOUR OF NICKEL BASED SUPERALLOYS

High temperature corrosion of coated and uncoated IN738LC and uncoated CM247LC nickel based super alloys in chloride and vanadium environment were carried out. To create corrosive environment (i.e. chloride and vanadium environment) salts of required proportions of Na2SO4, NaCl and V2O5 were applied on both sides of samples and loaded into the furnace at 700°C and 900°C. The weight changes were noted and SEM analysis was done to determine the surface morphology of hot corroded samples. Electron Dispersive Spectroscopy (EDS) was used to determine different elements present in corroded samples of CM247LC and IN738LC in chloride and vanadium environments at 700°C and 900°C. The present study revealed that CM247LC is more susceptible to hot corrosion than IN738LC due to varying amount of chromium and tungsten which is explained by degradation mechanism. Coated IN738LC has more life span than that of other samples.

The Contribution of Neural Networks to Solve Corrosion Related Problems

This paper summarizes the results of various attempts to implement a neural network for solving corrosion problems. The first activity was aimed to develop a model able to predict crevice corrosion of stainless steel and related alloys in chloride containing media from long-term exposure tests. Second, the preliminary evaluation of a neural network approach for rapid prediction of naphthenic acid corrosion performance (NAC) of carbon and stainless steels in a crude oil distillation unit will be described. In this work, the neural network was trained on the basis of experimental data from laboratory experience. Finally, non-deterministic models based on artificial neural network (ANN) were developed to predict the corrosion rate of carbon steel in CO2 environment by elaborating laboratory and field data. NN models were developed and tested using, as an input, pattern physico-chemical variables typically met in empiric and mechanistic models as well as parameters apparently not involved in the corrosion phenomenon. Results confirmed the validity of the NN approach

Electrochemical corrosion behaviour of Pb-free Sn–8.5Zn–0.05Al–XGa and Sn–3Ag–0.5Cu alloys in chloride containing aqueous solution

The electrochemical corrosion behaviour of Pb-free Sn–8.5Zn–0.05Al–XGa and Sn–3Ag–0.5Cu alloys was investigated in 3.5% NaCl solution by using potentiodynamic polarization techniques. The results obtained from polarization studies revealed that there was a negative shift in the corrosion potential with increase in Ga content from 0.02 to 0.2 wt% in the Sn–8.5Zn–0.05Al–XGa alloy. These changes were also reflected in the corrosion current density ( I corr) value, corrosion rate and linear polarization resistance (LPR) of the four element alloy. However, for Sn–3Ag–0.5Cu alloy a significant increase in the corrosion rate and corrosion current density was observed as compared to the four element alloys. SIMS depth profile results established that ZnO present on the outer surface of Sn–8.5Zn–0.05Al–0.05Ga alloy played a major role in the formation of the oxide film. Oxides of Sn, Al and Ga contributed a little towards the formation of film on the outer surface of the alloy. On the other hand, Ag 2O was primarily responsible for the formation of the oxide film on the outer surface of Sn–3Ag–0.5Cu alloy.

High-speed anode dissolution of heat-resistant chrome-nickel alloys containing tungsten and rhenium: III. Chloride-nitrate solutions

The anodic dissolution rates of two heat-resistant tungsten (12 wt %) and tungsten and rhenium (8 wt % W : 6 wt % Re) alloys in chloride, nitrate, and chloride-nitrate (30 g/l NaCl : 120 g/l NaNO3) electrolytes have been compared. An excess of the critical current density i crit depending on the hydrodynamic conditions leads to (i) the decreasing dependence of the current efficiency on the current density and (ii) the independence of the dissolution rate on the solution content. The mass-transfer mechanism, which determines the dissolution rate and the structure of superficial layers at i > i crit, is discussed. Data on the chemical content of the surface layers depending on the machining modes are presented. The modes of the electrochemical dimensional machining (ECDM) of the parts made of these alloys are offered to attain the best performance parameters for machining.

The effect of Cu-rich sub-layer on the increased corrosion resistance of Cu– xZn alloys in chloride containing borate buffer

The electrochemical behaviour of Cu– xZn alloys, as well as their constituent metals, in a borate buffer containing chloride ions in the molar range from 0.01 to 1 M are studied. Characteristics of these materials under anodic polarization are compared and the composition and morphology of the corrosion products formed in the course of polarization experiment are analysed by SEM and EDS. X-ray photoelectron spectroscopy and electrochemical impedance measurements are used for characterization of the surface layers formed on Cu, Zn and Cu–40Zn alloy during 2-h immersion at E oc in a borate buffer containing two different concentrations of chloride ions. New aspects of the behaviour of brass under E oc condition are revealed. The improved corrosion resistance of brass in chloride media, if compared to zinc metal, is attributed to a Cu-rich layer formed by the selective dissolution of zinc. Based on the results, a structural model describing the improved corrosion resistance of Cu–40Zn alloy with respect to Zn metal is proposed.

Corrosion-resistant amorphous aluminum alloys and structure of passive films

The corrosion behavior of amorphous Al-Ti-Ni, Al-Cr-Ti and Al-Cr-Mo alloys in 1 M HCl and that of amorphous Al-Ti-Mg alloys in chloride containing neutral solution is investigated. The amorphous Al-Ti-Ni, Al-Ti-Cr and Al-Cr-Mo alloys are passivated spontaneously even in 1 M HCl and show lower corrosion rates and higher pitting potentials in comparison with Al-Ti and Al-Cr binary alloys. Al-Ti-Mg alloys containing relatively low concentration of magnesium possess a better resistance against pitting corrosion. X-ray photoelectron spectroscopy measurement reveals that titanium and chromium are enriched in the passive films formed on Al-Ti-Ni, Al-Ti-Mg and Al-Cr-Mo alloys, respectively. Angle-resolved XPS measurements were performed in order to characterize the in-depth distribution of constituents in the passive films formed on amorphous Al-Ti-Ni, Al-Ti-Mg and Al-Cr-Mo alloys in the passive films of which, passivating elements are enriched.

Crevice corrosion: a neural network approach

Crevice corrosion of stainless steels and related alloys in near neutral chloride containing environments is a very widespread form of localised corrosion in industrial plants where sea water is a common coolant medium and the complexity gives rise to many types of potentially dangerous crevices. Crevice corrosion, like other modes of localised corrosion, is a stochastic process which should be treated using probability laws and concepts. Many test methods have thus far been proposed and several different models have been developed to study crevice corrosion phenomena. However, much remains to be done and to be understood before this problem can be fully solved. The complexity of the processes occurring during the onset and development of crevice corrosion, as well as the poor reliability of the above mentioned test methods, have led to the development of artificial intelligence systems. Among these, the artificial neural network (NN) system appears to be a powerful tool to tackle situations in which a large number of data are available but no simple models are derived. In the present paper an attempt to develop a NN for rapid predictions of crevice corrosion performance of alloys in chloride containing environments is described.

Relationship Between Conventional Pitting and Protection Potentials and a New, Unique Pitting Potential

Abstract A literature review was performed to identify test methods that have been used to examine pitting susceptibility of stainless steels and nickel-base alloys in chloride (Cl−) containing env...

New stainless steels for sea‐water applications. Part II: Comparison of corrosion and mechanical properties of laboratory and commercial ELI ferritic and superaustenitic stainless steels

AbstractThis paper represents a follow‐up to the first part of the work on new stainless steels for sea‐water service. Four laboratory ELI (Extra Low Interstitial) ferritic stainless steels (types 25 Cr‐4 Ni‐4 Mo), two commercial ELI ferritic stainless steels (types 25 Cr‐4 Ni‐4 MoTi and 26 Cr‐2.5 Ni‐3 MoTi) and two highly alloyed austenitic stainless steels (types 20 Cr‐25 Ni‐4.5 MoCu and 20 Cr‐18 Ni‐6 MoN) have been investigated.With a view to establish the performance of these new alloys in chloride containing environments, systematic electrochemical and laboratory exposure tests have been carried out to define how various factors affect its susceptibility to intergranular, pitting, crevice and stress corrosion. Tension tests were also performed.From the comparison of the localized corrosion resistance and mechanical properties it has been concluded that the laboratory Ti, Ti + Nb or Nb stabilized ELI ferritic stainless steels and the commercial type 25 Cr‐4 Ni‐4 MoTi of analogous composition could be a valuable alternative to the more expensive highly alloyed stainless steel type 20 Cr‐25 Ni‐4.5 MoCu which has been especially developed and already used for industrial sea‐water applications.

Dissolution behavior of high-purity Al-In alloy

Aluminum can effectively be debased by the addition of a small amount of indium or tin.This paper describes the experimental results for anodic dissolution of high-purity Al-In binary alloys in chloride solutions.At first, cast alloys having various indium contents were galvanostatically electrolyzed for 300 hrs. in synthetic sea water at a constant anode current density of 1 mA/cm2. Anode potential of 0.1% In alloy was constant at-1.1V (SCE) and its anode efficiency was found to be about 90%.Secondly, alloys, containing 0.010.2% In, were cold rolled to 90% reduction and subjected to solution heat-treatment at temperatures of 470620°C. subsequently, they were galvanostatically electrolyzed at a constant current density of 1 mA/cm2 for 1 hr. in 1M-NaCl (pH = 5.5) at 25°C. Stationary anode potential was measured and after anodic dissolution for 1 hr., dissolution morphology of alloys was examined.The dissolution was pitting and anodic behavior of alloys was found to be classified into two groups.Anode potential of alloys, solution-treated at temperatures lower than 500°C, was slightly less noble than that of 99.99% Al (-0.7V, SC E). While, alloys, containing more than 0.06% In and quenched from above 500°C, showed less noble anode potential of -1.1V.The shape of pits produced on pure aluminum was a rugged polyhedron having facets of {100} planes. The pit morphology of thin foils was examined under a transmission electron microscope and it was found that the process of pit growth was tunneling, by which (100) plane as an active front proceeded in [100] direction. Such a crystallographic growth of pits by tunneling was more remarkable in alloys showing dissolution at a potential more noble than -w0.9 V (A-type dissolution). Facets of the pits developed on the alloys, dissolved at less noble potential of -1.1 V (B-type dissolution), included {111} and other planes as well as {100} planes.Anodic behavior of the alloy having air-formed film was compared with that of the alloy treated in pure water at 30°C for 72 hrs. and very little difference was found in pitting behavior in the chloride solution between the both.