Aluminum Carbon Steel Research Articles

Silver zirconium oxide cermet coatings spray deposited onto galvanized steel sheet for low temperature solar applications

A new type of cermet coating, with potential use as low-cost solar thermal absorber has been developed using spray pyrolysis. It consists of crystalline silver nanoparticles embedded in amorphous zirconia and was obtained by spraying aqueous precursor solutions onto aluminized carbon steel sheets at 200 °C. It was found that simultaneous spraying of silver and zirconium solutions led to a considerable reduction, in the nanometer range, of silver particle size distribution. Hence, we comparatively studied the cermet coatings obtained by A) sequentially or B) simultaneously spraying silver and zirconium solutions. For the latter case, a zirconia anti-reflection layer was sprayed on top. Both coating systems were studied by SEM, AFM, HRTEM/EDS and UV-VIS-IR spectroscopy with respect to silver particle size distribution. Optical parameters like solar absorptance (AM 1.5) and thermal emittance (373 K) were determined from absolute hemispherical reflectance, and a performance coefficient was calculated in order to evaluate the solar selectivity of the coatings. The comparison showed that smaller silver particles lead to an increase in solar selectivity and that the size reduction is due to an effective encapsulation by zirconia of the silver particles when spraying silver and zirconium precursors simultaneously. Furthermore, HRTEM confirmed the metallic and crystalline state of the silver nanoparticles embedded in amorphous zirconia.

Research on Adhesion and Properties of Composite Coating on Aluminized Carbon Steel

In this paper, we studied the adhesion and properties of the composite coating on aluminized carbon steel. The part of the review introduces the concept and application of aluminizing technology and composite coating on carbon steel, and the related research is summarized. In the professional content section, the aluminizing process of carbon steel, the preparation method and characteristics of the composite coating, and the evaluation method of composite coating performance are introduced. In the main body, we focused on the research content of aluminized structure and corrosion behavior of carbon steel and studied the adhesion, corrosion resistance, wear resistance, thermal stability, and microstructural properties of composite coatings on aluminized carbon steel. In addition, this study includes the bonding mechanism between the composite coating and the substrate, the corrosion protection mechanism of the composite coating, the wear resistance mechanism of the composite coating, the thermal stability of the composite coating, and the factors affecting the adhesion, corrosion resistance, wear resistance, thermal stability and microstructure of the composite coating. The results show that the composite coating after aluminizing treatment can effectively improve the surface properties of carbon steel. Different preparation methods and process conditions have a significant effect on the performance of the composite coating. This study is of great significance for understanding the properties and preparation of composite coatings after aluminizing treatment of carbon steel.

Corrosion behavior of HDA (hot-dip aluminized) carbon steel C45 half immersed in molten salts (NaCl, Na2SO4) isothermally at 973 K

Aluminized carbon steel C45 samples of 0.44 wt.% carbon content were immersed half in a molten salt mixture (NaCl + Na2SO4 with a ratio of 1:3) at a temperature of around 973 K over three different exposure periods: 8, 24, and 72 h. It was observed that a new intermetallic layer (emergent layer) formed at the interface between the steel substrate and the pre-formed intermetallic layers as a result of further outward and inward diffusion of Al, Fe, and C, as indicated by a metallographic study involving SEM combined with EDS spot analysis and elemental analysis. It was also observed that flake-like new phases precipitated in both halves, largely composed of Fe–Al–C–O elementary components, where presumably, the steel C45's high carbon content and the prolonged exposure to high temperatures contributed to further chemical reactions between the elements of HDA specimens and the molten salts’ aggressive Cl and S elements. Moreover, they accelerated the rate of oxidation/corrosion of the hot-dip aluminized C45 steel specimens at high temperatures. Gibbs free energies calculations of some of the corrosion products confirmed the composition of the oxide scale detected experimentally.

NANOWIRE OXIDE FILM FOR LOW-TEMPERATURE ALUMINIZED 20 STEEL BY THERMAL OXIDATION

An aluminized coating for low-carbon steel with good corrosion and wear resistance was first prepared through low-temperature pack aluminization. Then, the low-temperature-aluminized steel substrate was subjected to thermal oxidation in air. The phase composition, surface morphology, roughness, and elemental distribution of the aluminized carbon steel both before and after thermal oxidation were analyzed through X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion resistance and wear resistance of the original carbon steel substrate, aluminized carbon steel, and oxidized carbon steel were tested. Results showed that nanowires composed of iron oxide and alumina formed in situ on the top layer of the aluminized carbon steel. The corrosion resistance and wear resistance of the low-carbon steel with the nanowire oxide coating were better than those of the original carbon steel and aluminized carbon steel because the in-situ nanowire oxide film improved the density of the aluminized coating.

Corrosion of Carbon Steel with and without Aluminized Coating in (O, S, H)-containing Gases at 500-800℃

The carbon steel formed the thick, somewhat porous, loosely adherent iron oxide scale when oxidized at 500-800℃ for 15 h in air. It formed the thicker, more porous, nonadherent scale consisting of FeS plus iron oxides in Ar/1%SO₂-mixed gas. It formed the much thicker, more porous, nonadherent scale consisting of FeS plus iron oxides in Ar/0.1% H₂S-mixed gas. However, the aluminized carbon steel formed the thin, protective Al₂O₃ surface scale even in Ar/1%SO₂-, and Ar/0.1%H₂S-mixed gas. Aluminizing drastically improved the corrosion resistance in (O, S, H)-containing gas.

Competitive graphitization and diamond growth on hot-dip aluminized carbon steel substrate

Abstract When carbon steel is directly exposed in 99%H 2 –1%CH 4 gas mixture for plasma enhanced CVD deposition of diamond coatings, an intermediate graphite layer is preferentially formed on the substrate surface, and the substrate is subjected to a severe internal carburization attack. The diamond coatings formed easily delaminate from the steel substrate. Hot dip aluminizing treatment of the carbon steel has markedly promoted diamond nucleation, growth and interfacial adhesion. The formation of graphite intermediate phase on the substrate surface is effectively inhibited and the substrate carburization is also suppressed. The possible mechanism of this transition is discussed based on a series of analytical techniques.

The Influence of Temperature on the Oxide Layer Formation of Aluminized Carbon Steel

The growth of thin oxide layer due to the variation in temperature on the surface of aluminized carbon steel was investigated. Hot dip aluminizing of low carbon steel was carried out at 750 °C in a molten pure aluminum for 5 minutes. Aluminized samples were heat treated at 600 °C, 700 °C, 800 °C, and 900 °C for 1 hour. The formation of aluminum oxide layer was investigated in this study. Optical microscopy, Atomic Force Microscopy (AFM), SEM and EDAX were used in investigation. From the observation, the appearance of aluminum oxide layer increased with the increase in temperature. The result of EDAX analysis revealed the existence alumina phase. Surface roughness measurement showed increment with the increase in oxidation heat treatment temperature.

Corrosion of Carbon Steel and Alloys in Concentrated Ammonium Chloride Solutions

Corrosion resistance and the behavior of carbon steel and alloys in high concentration ammonium chloride (NH4Cl) solutions were investigated. This study was conducted to better understand material performance in severe NH4Cl corrosive environments in refineries. Immersion tests were performed under boiling 20 wt% and 40 wt% NH4Cl solutions. Sixteen materials commonly used in refineries and two new alloys were examined, including carbon steel; aluminized carbon steel; aluminum brass; Types 405, 410, 304L, 316L, and 321 stainless steels (UNS S40500, S41000, S30403, S31603, and S32100); 300-series stainless steel with 6% Mo; two types of super duplex stainless steels; Alloys 800, 625, and C-276 (UNS N08800, N06625, and N10276); Grade 2 and Grade 19 titanium (UNS R50400 and R53530); Alloy A (equivalent to a modified Type 317L [UNS S31703] stainless steel); and a modified Alloy 825 (UNS N06845). Significant corrosion was observed in carbon steel in both solutions. The corrosion rates of carbon steel were as high as 25.4 mm/y and 60.4 mm/y in 20 wt% and 40 wt% NH4Cl solutions, respectively. However, neither general corrosion nor pitting was observed on titanium alloys and alloys with a pitting resistant equivalent number (PREN) of 40 and higher. The maximum pit depth had a close relationship with the PREN. In addition, an electrochemical study was used to investigate the corrosion behavior of carbon steel. The effects of the temperature and NH4Cl concentration were determined from polarization curves and the corrosion potential.

Effect of Relative Humidity on Ammonium Chloride Corrosion in Refineries

Abstract Corrosion behavior and the hygroscopic properties of solid ammonium chloride (NH4Cl) salt were investigated. This study was conducted to determine the root cause of significant corrosion caused by NH4Cl salt deposition in reactor-effluent streams in hydroprocessing units. Corrosion and water absorption tests were performed under various relative humidity (RH) conditions with solid NH4Cl salts using a temperature and humidity control chamber. Eight types of materials commonly used in refineries were examined, including carbon steel (UNS K02702), Type 304 (UNS S30400) stainless steel, duplex (UNS S39274) stainless steel, Grade 2 titanium (UNS R50400), Alloy 400 (UNS N04400), Alloy C-276 (UNS N10276), aluminum brass (UNS C68700), and aluminized carbon steel (hot-dip aluminized UNS K02702). Significant corrosion was observed around 60% RH on all the alloys except Alloy C-276. Carbon steel corroded above 20% RH. Its highest corrosion rate was observed at 60% RH and 80°C. Type 304 stainless steel and d...

Nanocrystallization of aluminized surface of carbon steel for enhanced resistances to corrosion and corrosive wear

Aluminizing is often used to improve steel's resistances to corrosion, oxidation and wear. This article reports our recent attempts to further improve aluminized carbon steel through surface nanocrystallization for higher resistances to corrosion and corrosive wear. The surface nanocrystallization was achieved using a process combining sandblasting and recovery heat treatment. The entire surface modification process includes dipping carbon steel specimens into a molten Al pool to form an Al coat, subsequent diffusion treatment at elevated temperature to form an aluminized layer, sandblasting to generate dislocation network or cells, and recovery treatment to turn the dislocation cells into nano-sized grains. The grain size of the nanocrystallized aluminized surface layer was in the range of 20–100 nm. Electrochemical properties, electron work function (EWF), and corrosive wear of the nanocrystalline alloyed surfaces were investigated. It was demonstrated that the nanocrystalline aluminized surface of carbon steel exhibited improved resistances to corrosion, wear and corrosive wear. The passive film developed on the nanocrystallized aluminized surface was also evaluated in terms of its mechanical properties and adherence to the substrate.

アルミニウム箔を利用したステンレス鋼の高温アルミナイジング処理

The alloy layer formation during high-temperature aluminizing at diffusion temperature TD from 1073 to 1273K in air was investigated for austenitic, ferritic and martensitic stainless steels. The void accumulation was observed in FeAl and αFe interface in high-temperature aluminized carbon steel, while in all stainless steels that were not observed. The alloy layers observed in stainless steels at TD=1073K for the diffusion time t=0.6 ks were Fe2Al5 and Al8Cr5. With increasing TD and t, FeAl layer and αFe layer appeared. As TD and t increased further, Fe2Al5 disappeared, and finally become only two layers FeAl and αFe.

Study on high-temperature naphthenic acid corrosion and erosion-corrosion of aluminized carbon steel

High-temperature naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behaviors of pack-aluminized carbon steel have been investigated in laboratory to evaluate the resistance of aluminized layer to the NAC and NAEC. A field erosion-corrosion test of 700 days was also performed in an oil refinery. Parallel tests were carried out for carbon steel. It was found that the aluminized steel exhibited a better NAC resistance only at early testing stage than the carbon steel in high total-acid-number (TAN) environment. The NAC resistance degraded rapidly with increasing testing time, and became even worse than that of the carbon steel at final testing stage, accompanying a step-like or lamellar spallation in the aluminized layer. In low TAN environment, the aluminized steel exhibited a much better resistance to both the NAC and NAEC in comparison with the carbon steel. Similarly a good erosion-corrosion resistance was found for the aluminized steel in actual oil-refining environment although relatively serious erosion-corrosion attack simultaneously took place in the aluminized layer. Based on the above results, possible NAC and NAEC mechanisms for the aluminized steel are discussed.

Erosion–corrosion of various oil-refining materials in naphthenic acid

A jet-impingement installation for high-temperature and fast-flow simulation of oil-refining environments has been designed and established. The optimum experimental parameters have been selected by considering both the numerical analysis results of the jet-impingement flow field and the practical aspects of system operation. The naphthenic acid erosion–corrosion (NAEC) resistance of carbon steel (CS), pack-aluminized carbon steel (AS) and molybdenum (Mo)-bearing stainless steels (SSs) were evaluated. It was found that increasing the fluid velocity and/or increasing the experimental temperature significantly aggravated NAEC, which may be attributed to the enhanced mass transfer and the accelerated corrosion reactions at surface active sites as well as the rapid spallation of corrosion products from the metal surface. Both the aluminized carbon steel and the stainless steels showed much better resistance against NAEC than the carbon steel. The NAEC resistance of the stainless steels increases with increasing molybdenum content. The possible reasons for the observed NAEC behavior are discussed.

Corrosion and erosion-corrosion behaviors of carbon steel in naphthenic acid media

The naphthenic acid corrosion (NAC) and erosion-corrosion (NAEC) behaviors of carbon steel were investigated detailedly in laboratory. The resistance to NAEC of pack-aluminized carbon steel and carbon steel coated by high velocity oxygen-fuel (HVOF) thermal-sprayed AISI 316L stainless steel, was also investigated in both laboratory and an oil refinery. It was found that the control-step of NAC was primarily dependent on the temperature. The NAC rate of carbon steel increased markedly with the increase of the total acid number and temperature, which may be attributed to the enhanced absorption and active reaction of naphthenic acid molecules on the metal surface. Increasing the velocity of flow seriously aggravated NAEC, especially in the high temperature range. The reasons were closely associated with the enhanced mass transfer and the accelerated active reaction as well as the rapid spallation of corrosion products from the metal surface. Both the aluminized carbon steel and the carbon steel covered by HVOF coating showed better resistance against NAEC compared to the carbon steel due to higher microhardness and corrosion resistance of their surface-layers. The HVOF coating is hopeful to be applied for NAEC prevention of the components in oil refineries in view of present experimental results.

Effectiveness of aluminizing in machine construction

1. Diffusion aluminizing sharply increases (300\2-600%) the thermal stability of heating equipment and machine parts of carbon steels, particularly rolled sections. 2. Our results failed to confirm the reported effectiveness of substituting aluminized carbon steel parts for heat-resisting steel parts in heating equipment. The carbon steel parts were put out of commission by severe warping resulting from reduced strength. 3. Heat-resisting steels can be replaced with aluminized carbon steels only in the case of parts not subject to mechanical loading. 4. Aluminizing is not expedient for parts made of heat-resisting chromium-nickel steels intended for prolonged operation at high temperatures because the aluminum gradually diffuses into the depth of the piece, which sharply reduces the aluminum concentration in the surface.