Liquid Aluminum Research Articles

How the Chemistry of Raw Materials Affects Aluminum Produced in Cells with Prebaked Anodes

This paper analyzes how major impurities found in raw materials affect the chemistry of primary aluminum. Alumina and prebaked anodes tend towards lower quality due to the depletion of natural sources of high-quality bauxites and using low-quality carbon to make prebaked anodes (PA). The authors analyzed the chemistry of raw materials supplied for electrolysis. The paper shows the investigated upward trends in the presence of Fe and Si impurities in alumina and prebaked anodes, which jeopardizes the aluminum production process. The increased presence of such materials worsens the chemical composition of the resulting liquid aluminum. If the finished product is to be of high quality, alumina and PA mast contain, respectively (wt.%): 0.010 and 0.024 Fe, 0.013 and 0.022 Si. The proposed idea is to categorize the alumina in storage. Alumina from different manufacturers must then be batched in such a way as to have consistent, ‘averaged’ chemistry before going to electrolysis cells.

In-situ Al3Ti particle reinforcement for stiff aluminum die castings

The intermetallic phase Al3Ti is a promising candidate to increase the stiffness of aluminum casting alloys due to its high Young’s modulus. Reinforcement particles are formed by the in-situ reaction between solid titanium particles and the liquid aluminum melt. A high-shear mixer is used to peel off the reaction layer on the surface of the Ti particles and distribute the Al3Ti particles homogeneously in the melt. This work investigates the dissolution velocity of different size fractions of Ti powder in three different aluminum casting alloys. The results were used to fabricate specimens with different volume fractions of Al3Ti particles by high pressure die casting. Microstructure characterization was performed to investigate the distribution of the Al3Ti particles within the castings. The mechanical properties were determined by tensile tests and resonant frequency analysis.

Ultrafast atomic view of laser-induced melting and breathing motion of metallic liquid clusters with MeV ultrafast electron diffraction

Under the irradiation of an ultrafast intense laser, solid materials can be driven into nonequilibrium states undergoing an ultrafast solid-liquid phase transition. Understanding such nonequilibrium states is essential for scientific research and industrial applications because they exist in various processes including laser fusion and laser machining yet challenging in the sense that high resolution and single-shot capability are required for the measurements. Herein, an ultrafast diffraction technique with megaelectron-volt (MeV) electrons is used to resolve the atomic pathway over the entire laser-induced ultrafast melting process, from the initial loss of long-range order and the formation of high-density liquid to the progressive evolution of short-range order and relaxation into the metastable low-density liquid state. High-resolution measurements using electron pulse compression and a time-stamping technique reveal a coherent breathing motion of polyhedral clusters in transient liquid aluminum during the ultrafast melting process, as indicated by the oscillation of the interatomic distance between the center atom and atoms in the nearest-neighbor shell. Furthermore, contraction of interatomic distance was observed in a superheated liquid state with temperatures up to 6,000 K. The results provide an atomic view of melting accompanied with internal pressure relaxation and are critical for understanding the structures and properties of matter under extreme conditions.

Numerical Analysis of Microstructure Anomalies during Laser Welding Nickel-Based Single-Crystal Superalloy Part I: Salient Aluminum Redistribution Melioration

Correlation between welding conditions, such as laser power, welding speed and welding configuration, microstructure anomalies, including columnar/equiaxed transition (CET) and stray grain formation, and metallurgical factors, such as aluminum redistribution and supersaturation near dendrite tip, is elucidated by thorough numerical analysis to explain prevalent phenomenon of insidious microstructure development and face the challenge of microstructure amelioration as well as solidification cracking resistance improvement during course of ternary single-crystal Nickel-Chromium-Aluminum superalloy melt-pool solidification for crack-free laser surface modification. Metallurgical factors of γ gamma phase microstructure development strongly depend on welding configuration, and heat input is not as important as welding configuration. Although melted-pool center region is susceptible to microstructure anomalies, (001)/[100] welding configuration possesses auspicious growth crystallography under which the bimodal profiles of solid aluminum concentration and liquid aluminum supersaturation ahead of dendrite tip are symmetrically distributed to potentially decrease solute redistribution and increase resistibility to solidification cracking. Dissimilarly, (001)/[110] welding configuration possesses insidious growth crystallography under which the profiles of solid aluminum concentration and liquid aluminum supersaturation ahead of dendrite tip are asymmetrically distributed to preferably facilitate alloying plentiful enrichment and differentiate problematical microstructure instability on half side of molten pool. In the bottom of molten pool, beneficial Al-barren [001] dendrite is kinetically driven by homologous single-crystal epitaxial growth without columnar/equiaxed transition. On the right side of molten pool, detrimental Al-rich [100] dendrite is spontaneously susceptible to stray grain formation with equiaxed morphology. Symmetrical microstructure development is more enrichment-resistant than asymmetrical microstructure development, which is crystallographically ascribable to favorable thermo-metallurgical factors, i.e. aluminum redistribution mitigation and supersaturation relief, and substantially reduce metallurgical degradation and microstructure failure. The faster welding speed and the lower laser power are used, the smaller aluminum concentration and supersaturation ahead of dendrite tip are kinetically incurred to suppress columnar/equiaxed transition and stray grain formation with a number of thermometallurgical factors contribution to considerable microstructure amelioration and increasingly improve solidification cracking resistance and vice versa. Shallow molten-pool shape with symmetrical growth crystallography efficiently advances anomalies-resistant microstructure development with diminution of partition driving forces for solute redistribution and supersaturation during nonequilibrium solidification instead of deep molten-pool shape with asymmetrical growth crystallography. The latter importantly aggravates stray grain formation. Useful combination of optimum solidification conditions and favorable growth crystallography predominantly minimizes diffusion-controlled solute deviation and microstructure anomalies for excellent single-crystal superalloy laser processing without cracking, and possesses tenable relationship between welding conditions, solute redistribution and microstructure anomalies. The mechanism of crystallography-aided concentration fluctuation and copious supersaturation behind prominent phenomenon of microstructure anomalies, where nucleation and growth of stray grain formation near dendrite tip are activated, is consequently proposed. The comparison between numerical analyses and experiment results are valid and satisfactory. Microstructure anomalies are predictable for proper understanding of multicomponent microstructure development in the interior of fusion zone. The theoretical methodology is reproducible as consequence of availability of thermodynamic and kinetic properties of Nickel-based or Iron-based single-crystal superalloys.

The Effect of Rotary Degassing Treatments with Different Purging Gases on the Double Oxide- and Nitride Film Content of Liquid Aluminum Alloys

Rotary degassing is one of the most frequently used melt treatment technologies used for processing liquid aluminum alloys. Despite this, the information available about the possible effects of this method on the double oxide- and nitride film (bifilm) content, especially when using different purging gases, is quite limited. For this reason, in this study, the effects of multiple rotary degassing treatments conducted with N2 and Ar purging gases on the bifilm quantity of a casting aluminum alloy were compared. The characterization of the melt quality was realized by the computed tomographic (CT) analysis of reduced pressure test (RPT) specimens, image analysis, and scanning electron microscopy (SEM) of the fracture surfaces of K-mold samples. Based on the results, by the application of Ar as a purging gas, relatively low bifilm content can be achieved. On the other hand, while the use of N2 leads to the formation of numerous small-sized nitride bifilms, which significantly increased the pore number density inside the RPT specimens. This can be associated with the nitride formation by the chemical reaction between the liquid aluminum alloy and the N2 purging gas bubbles during the degassing treatments.Graphical abstract

Filtration resistance during pressure filtration tests of liquid aluminium alloys

Abstract Prefil Footprinter, a portable pressure filtration instrument, is usually employed to detect liquid metal quality. However, no investigations have ever been done to determine overall filtration resistance and resistance of the “clean” filter media. Based on the identification of flow behaviour using the derivative methods, classic filtration equations have been effectively used to estimate total filtration resistance for the first time. The variations of overall resistance during filtration provide a new approach to understand filtration behaviour. The resistance values of the “clean” filter media have been obtained for the first time. An innovative method has been developed to obtain the resistance of the “clean”' filter media through the backward extrapolation of the overall filtration resistance versus filtrate weight or filtration time curves over the steady stages operating in incompressible cake mode.

Thermodynamic modelling of the Ce–Ni system

Abstract The phase equilibria in the Ni-rich part of the Ce–Ni binary system were re-determined using DTA, metallography and SEM/EDX. CeNi5+x presents a Ni solubility up to x = 0.53 at 1073 K. The melting point of CeNi5 is 1608 ± 5 K and the CeNi5+x –Ni eutectic has been observed at 1477 ± 5 K and x(Ni) = 0.91. The enthalpy of formation of stoichiometric CeNi5 has been measured by drop dissolution calorimetry in liquid aluminium and a value of Δf H = – 29.1 ± 2.2 kJ/moles of atoms was derived. Based on this new experimental data and literature values, a complete thermodynamic modelling of the Ce–Ni diagram was performed.

Hydrogen Solubility in Liquid and Solid Pure Aluminum—Critical Review of Measurement Methodologies and Reported Values

Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties and performance of pure aluminum and aluminum alloy products. Unfortunately, there is a significant disparity between published values of hydrogen solubility in pure aluminum and aluminum alloys. This is because the measurement of the extremely low soluble hydrogen concentration in aluminum and its alloys is experimentally difficult. Also, the reproducibility, accuracy, and reliability of the hydrogen solubility values are very sensitive to the measurement techniques, test conditions, chemical composition, and state of the aluminum sample. Thus, no serious discussion of the reliability of reported values of hydrogen solubility in aluminum and its alloys can be undertaken without a critical assessment of the fundamental principles of the experimental techniques used in the determination of the reported values. In this article, a critical review of the fundamental principles of the experimental techniques used in the measurement of hydrogen solubility in liquid and solid pure aluminum and aluminum alloys is presented. In addition, the reliability and possible accuracy of reported values of hydrogen solubility in solid and liquid pure aluminum are critically assessed. Empirical equations for calculating hydrogen solubility in liquid and solid pure aluminum as a function of temperature and pressure, derived from the most reliable sets of data are recommended. At 101.3 kPa (1 atm.) hydrogen partial pressure, the most reliable values of hydrogen solubility at the melting point (833 K) of pure aluminum are 0.71 cm3/100g (i.e., 6.32 × 10-5 wt.% H) and 0.043 cm3/100g (i.e., 3.81 × 10-6 wt.% H), in the liquid and solid state, respectively. So, the partition coefficient of hydrogen in pure aluminum is 0.061.

Исследование структурной неоднородности расплава алюминия методом акустической эмиссии

Acoustic emission (AE) is experimentally investigated when the temperature of the aluminum melt changes. The Fourier analysis is carried out of the amplitude-frequency spectrum of AE signals in the temperature range of 665-860 ° C In the studied frequency range, periodic repetition of signals with maximum intensity was established. It is assumed that the acoustic spectrum of the signals is associated with structural rearrangements in the melt and reflects the transformation of the local order in liquid aluminum. Dynamics of changes in the intensity of AE signals with an increase in the melt temperature suggests that the local order in the melt inherits the structure of the crystalline precursor. The paper analyzes the process of cluster formation during melt cooling. Based on the above, the concepts of the melt structure as a partially ordered cluster environment are discussed.

The effects of coagulant types on the quality and added value of raw rubber materials

Many processing problems still occur, causing the low quality of raw rubber materials and farmers low-income. This can be seen from the use of coagulants, storage methods and the level of cleanliness. This study was aimed at analyzing the quality and added value of raw rubber materials based on the use of coagulant types. This study was conducted in October - November 2021. Fresh latex was obtained from the rubber plantation in Mulyaguna Village, OKI Regency. Completely randomized design was used with 5 treatments and 4 replications. The coagulants used were the recommended ones (liquid smoke, formic acid), and the commonly used by the farmers (sulfuric acid, aluminum sulfate, and TSP fertilizer). The results of the study showed that liquid smoke and formic acid were better than the coagulants commonly used by farmers, which could be seen from the ash content, initial plasticity, and plasticity retention index. The dry rubber contents (DRCs) using liquid smoke, formic acid, sulfuric acid, aluminum sulfate, and TSP fertilizer were 66.081; 62.978; 59.067; 56.202 and 60.796 respectively. Liquid smoke and formic acid provided the added value for raw rubber materials of 1,203/kg IDR and 792/kg IDR compared to sulfuric acid commonly used by farmers.

Influence of modification with highly dispersed silicon carbide on the casting properties of the secondary alloy of the Al-Si system

One of the main areas of application of aluminum is the aerospace and transport industries, which are constantly increasing the requirements for the properties of cast products. The use of aluminum as the main material for the manufacture of various parts of vehicles can significantly reduce their weight, which leads to a decrease in fuel consumption. In order to meet the requirements of the modern world, the work considers studies to improve the quality and increase the properties of products from the secondary aluminum alloy AlSi12. Modern technologies for processing liquid aluminum alloy are analyzed. According to the results of an analytical review, it was found that modifiers that affect the size of the primary grain and the shape of inclusions of eutectic silicon are of the greatest interest. It was found that the modification processes do not change the chemical composition of the alloy, but rather contribute to a change in the size and shape of the structural components of the alloy. The paper considers the influence of an ultradispersed SiC modifier with a particle size of up to 200 nm on the casting properties of secondary aluminum alloys: fluidity, linear and volumetric shrinkage. The fluidity was studied in green sand and metal mould. It was found that the addition of 0.1 % SiC improves the fluidity of the secondary alloy from 560 to 630 mm for green sand mould and from 230 to 295 mm for a metal mould due to cleaning from non-metallic inclusions. A further increase in the SiC content to 0.2 % does not lead to an obvious increase in fluidity. The study of linear shrinkage found that increasing the content of the modifier to 0.2 % contributes to its decrease. At the same time, an increase in the pouring temperature of the alloy promotes an increase in the total linear shrinkage, which is associated with the long residence time of the metal in the liquid state. As a result of the rapid crystallization of the melt with additional nucleation centers in the role of which are particles of the ultradispersed modifier, the coefficient of volumetric shrinkage decreases from 28 to 20 %. The proposed technical solutions for the modification of alloys of the secondary alloy AlSi12 can be used in processes that will improve the quality of cast metal products with the economical use of energy resources and materials for its production.

A Hybrid Modeling Method for Aluminum Smelting Process Based on a Hybrid Strategy-Based Sparrow Search Algorithm

In the production of aluminum, the regenerative aluminum smelting process is an important part for energy efficiency and product quality. Aluminum liquid temperature is a significant variable in the aluminum smelting process, and it is costly to measure timely because it requires protective temperature sensor. To handle this problem, a kind of modeling framework which combine a mechanism model with multi-scale kernel technique is proposed. First, the mechanism model is built for the aluminum liquid temperature by the energy conservation law and heat transfer mechanism. Since the mechanism model is based on some assumptions, it often results in unknown variables. Thus, the multi-scale kernel technique is used to obtain the unknown variables. Finally, a hybrid temperature prediction model is built by combining the multi-scale kernel and the mechanism model. The parameter identification of the hybrid model is described as an optimization problem, and a hybrid strategy-based sparrow search algorithm (HSSA) is proposed to solve this problem. The experiment results show that HSSA has higher convergence accuracy and stronger global search ability than the original sparrow search algorithm (SSA), and the proposed hybrid model can correctly estimate the aluminum liquid temperature.

In English

Boron carbide (BC, B15-xCx B4C) has a unique combination of properties. This makes it a material for priority applications for a wide range of engineering solutions. The high melting point and heat resistance of the compound contribute to its use in refractory conditions. Due to its extreme abrasion resistance, B4C is used as an abrasive powder and coating. Due to its high hardness and low density, B15-xCx has ballistic characteristics. It is usually used in nuclear programs as an absorbent of neutron radiation Boron carbide ceramics (B15-xCx or BC) may lose strength and toughness due to the amorphization effect under high shear stresses. Aluminum dodecaboride AlB12 or B12Al, as well as boron carbide B12 [(CCC) x (CBC) 1-x] have common structural units B12 family of boron-icosahedral structures. The bond between icosahedrons is mainly due to atoms (Al, Si, O) or chains (CMC), where M is Al, Si, B, C. Doping BC powder with a small amount of AlB12, in cases of shock-shear stress, triggers the mechanism of "micro-cracking". Micro cracks and pores are formed in ceramics. The breakdown voltage decreases. AlB12 synthesis is associated with known difficulties. On the other hand. The production of metal-ceramic materials for several decades is associated with the interaction of liquid aluminum and boron nitride. The calculation of this reaction shows that it is exothermic. Avoiding oxidation in vacuum, the reaction occurs through the formation of aluminum nitride and aluminum dodeca-boride. In contrast to the liquid state, the process continues until the end, at conditional temperatures of evaporation of aluminum with slight changes in vacuum. The reaction product is a mixture of nanosized AlN/AlB12 powders with a weight ratio of 3/1 ready for baking without grinding. The acid-base properties of the nanosized powder mixture AlN + AlB12, the products of the interaction BN + Al in vacuum, which are used optionally, emit separate in pure phases of aluminum nitride and aluminum dodeca-boride. The yield of AlB12 is ~ 25%, boron reaches ~ 100%. The average particle size of the AlB12 powders according to TEM and ACS X-rays (area of coherent X-rays scattering), L (nm) is LTEM=110-150nm, LACS=51-70nm. The average specific surface area of the powder according to BET, TEM and ACS, SBET.m2/g=21,0-15,0; STEM.m2/g=21,4-15,4; SACS.m2/g=46,1-33,6; (at 1460 and 1640K, respectively).

Probing the self-diffusion process in Aluminium.

An in-depth understanding of the diffusion process in liquid metals is a key to design and engineering new high-performance materials. In this study, using molecular dynamics simulations supplemented with the embedded atom potential, we investigate/compare the self-diffusion process in liquid Aluminium. To understand the self-diffusion process, we analyse the radial distribution functions, velocity distributions, mean square displacements, and self-diffusion coefficients at various temperatures well above the melting temperature of Aluminium in the temperature range of 1000 K to 1800 K. As a key result, in both the [Formula: see text] and [Formula: see text] phases, the self-diffusion coefficients show a non-linear variation with rise in temperatures in the range of 1000 K to 1200 K. From 1300 K to 1800 K, the self-diffusion coefficients increase more or less monotonically with rise in temperature. We found that a higher temperature in the range of 1300 K to 1800 K leads to a greater self-diffusion coefficient, suggesting the more violent movement of the atoms around their equilibrium positions. The results presented in this work can help to understand the differences in the self-diffusion process in the technologically relevant Al phases.

Performance of TiB2 Wettable Cathode Coating

A TiB2 wettable cathode coating was deposited on a graphite carbon cathode material via atmospheric plasma spraying (APS). The microstructure and phase composition of the TiB2 coating were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The wettability and corrosion resistance of the coating were studied in a molten-aluminum electrolytic system. The results showed that the surface of the TiB2 coating prepared via plasma spraying was flat and that the main phase of the coating was TiB2. The wettability between the TiB2 coating and liquid aluminum was better than that between graphite cathode carbon block and liquid aluminum. The abilities of the TiB2 coating and graphite cathode carbon block to resist sodium (Na) penetration and prevent molten salt corrosion were compared through a corrosion test. The TiB2 coating was found to have better resistance to Na penetration and better refractory cryolite corrosion resistance than graphite cathode carbon block.

Formation of Complex Inclusions in Gear Steels for Modification of Manganese Sulphide

Suitable MnS inclusions in gear steel can significantly improve the steel machinability and reduce the manufacturing costs. Two gear steel samples with different sulphur contents were prepared via aluminium deoxidation followed by calcium treatment. The shape, size, composition and percentage distribution of the inclusions present in the steel samples were analyzed using an electron probe micro-analysis (EPMA) technique. The average diameter of MnS precipitated on an oxide inclusion is less than 5 µm. It was found that the steel with high sulphur content contains a greater number of elongated MnS precipitates than low sulphur steel. Moreover, there are more oxide inclusions such as calcium-aluminates and spinels with a small amount of solid solution of (Ca,Mn)S in low content sulphur steel after calcium treatment, which indicates the modification of solid alumina inclusions into liquid aluminates. The typical inclusions generated in high sulphur steel are sulphide encapsulating oxide inclusions and some core oxides were observed as spinel. The formation mechanisms of complex inclusions with different sulphur and calcium contents are discussed. The results are in good agreement with thermodynamic calculations.

Modeling the Filler Phase Interaction with Solidification Front in Al(TiC) Composite Produced by the In Situ Method.

This paper presents simulation results of the interaction of TiC nanoparticle in liquid aluminum. The behavior of the TiC particle in the frontal interaction region stems from the operation of a system of such forces as gravity, viscous flow drag force, and Saffman force. The difference in density between the TiC and the aluminum matrix makes the particle fall, regardless of the radius dimension; while the Saffman force—which accounts for the local velocity gradient of the liquid aluminum—causes that particles with the smallest radii considered in the calculations 6.4 × 10−8 m; 7 × 10−8 m; 7.75 × 10−8 m; 9.85 × 10−8 m are repelled from the solidification front and the particles with 15.03 × 10−8 m are attracted to it. The viscosity growth in the course of casting caused by the lowering temperature reduces this effect, though the trend is maintained. The degree to which the particle is attracted to the front clearly depends on the velocity gradient of the liquid phase. For a very small gradient of 0.00001 m/s, the particle is at its closest position relative to the front.

Effect of Waste Titanium Chips Addition Into the Aluminum Alloys on Their Microstructure

In the present study, turning chips were preferred to add titanium into liquid aluminum. Although being easy to reach and cheap, the chips were thought to be effective in minor titanium addition with their large surface area. Experimental studies have been carried out with A356 casting alloy and commercial purity aluminum. The effects of different process parameters were investigated on titanium transfer efficiency, microstructural and microhardness properties of the formed phases. The processes were carried out between 740 - 820 °C, for 2, 4, and 6 h, with the amount of added chips 5 and 10 wt.% (3 and 6 vol.%). The experiments were conducted with both commercially pure Al and A356 alloy. The microstructural investigations and microhardness measurements were carried out on the formed Al3Ti and (Al, Si)3Ti phases. The first noticeable result was that titanium transfer was more efficient in pure aluminum than in the A356 alloy. Also, it was observed that this difference became more significant with an increase in wt.% addition. The measured microhardness values were also differentiated depending on the Si content of the formed Al3Ti compound. Due to the presence of high Si content in A356 alloy, transference efficiencies of Ti were found highly limited compared to pure aluminum as the silicon enrichment in the Al3Ti compound reduces the diffusion of titanium and the growth rate of Al3Ti particles. Maximum transference efficiency was found 47.05% with 10 %wt. chip addition in commercially pure aluminum at the processing conditions of 780 °C for 4 h.

Purification of aluminium-silicon alloy by electromagnetic directional solidification: Degassing and grain refinement

• An electromagnetic directional solidification process was proposed to purify Al alloy. • Grain refinement and degassing were realized simultaneously. • Effects of the induction current, moving rate, and remelting were investigated. • Both tensile strength and elongation were improved by remelting process. • The mechanism of bubble transfer process was explained by simulation. The grain size and porosity are two significant parameters to evaluate the properties of the Al alloy. In this work, an electromagnetic-field-enhanced directional solidification process hybridized with the remelting treatment was proposed to refine the grain size of Al alloys and at the same time to remove the residual gas in molten alloys. Furthermore, the effects of several factors on the grain refinement and degassing were investigated. The high induction current is effective for the obtainment of the small homogeneous grain size because of the stirring effect. With the increase of the moving rate, the grain size increased and then decreased due to the nucleation effect. The remelting process enables both the grain refinement and H 2 degassing to obtain regular grain orientations. The simulated pressure field, velocity field and H 2 gas volume fraction show the mechanism of the bubble transfer in the liquid Aluminum alloy. The pressure field depicts a sharp pressure gradient on the upper side of the bubble. The velocity field indicates an increase in the velocity maximum in the bubble. The shape evolution process of the H 2 bubble shows the effect of the interface tension.

Effect of Electric Pulse Treatment on Hot-Dip Aluminizing Coating of Ductile Iron.

In this paper, hot-dip aluminizing of ferrite nodular cast iron was carried out after treating liquid aluminum with different electrical pulse parameters. Compared with that of conventional hot-dip aluminizing, the coating structure of the treated sample did not change, the surface was smooth and continuous, and the solidification structure was more uniform. When high voltage and large capacitance were used to treat the liquid aluminum, the thickness and compactness of the coating surface layer increased. The thickness of the alloy layer decreased, and, the compactness and the micro hardness increased, so the electric pulse had a certain inhibition on the formation of the alloy layer. The growth kinetics of the alloy layer showed that the rate-time index decreased from 0.60 for the conventional sample to 0.38 for the electric pulse treated sample. The growth of the alloy layer was controlled by diffusion and interface reaction, but only by diffusion. The AC impedance and polarization curves of the coating showed that the corrosion resistance of hot-dip coating on nodular cast iron was improved by electric pulse treatment.