Papers by Keyword: Corrosion

Abstract: Saturated polyester (PE) resin was modified with 0.5 and 1.0% (v/v) of epoxysilane-treated (aluminosilicate, muscovite, nepheline syenite, and wollastonite) and alkoxysilane-treated (aluminosilicate) mineral fillers before coating to carbon steel. The corrosion behavior of specimens was studied using potentiodynamic polarization method. Wetting behavior and adhesion of specimens were evaluated by static contact angle and cross-cut tape tests, respectively. The addition of silane-treated mineral fillers dramatically improved the corrosion resistance of saturated PE, with epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate at 0.5% concentration significantly lowering the corrosion tendency and rate in 2 M HCl solution. Meanwhile, only epoxysilane-treated nepheline syenite significantly increased the water contact angle of saturated PE. The adhesion of saturated PE to carbons steel was increased after addition of fillers at 0.5%, with epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate giving the lowest percent area removed after application of adhesive tape. Epoxysilane-treated wollastonite and alkoxysilane-treated aluminosilicate at 0.5% were found most suitable as fillers for saturated PE coating.

Abstract: Magnesium alloys inherently possess poor corrosion resistance. One of the surface modification techniques to improve the corrosion resistance of magnesium alloys is Micro Arc Oxidation (MAO). Application of RZ5 magnesium alloy in aircraft industries demands assured corrosion resistance of RZ5. The quality of the ceramic oxide coating developed by MAO is influenced by various operating parameters. In this study, oxide coatings on RZ5 Magnesium alloy were developed by MAO at two different frequency levels (100Hz and 1000Hz) and at two duty cycles (10% and 90%) at a constant current density of 0.06A/cm² for 15 minutes in a silicate based electrolyte (10g/l Na₂SiO₃.9H₂O + 4g/l KOH). Results showed that the coating produced with the combination of higher frequency and lower duty cycle exhibits a better corrosion resistance than the coating produced with other combinations of parameters.

Abstract: In this paper, the results of the structural analysis of glued laminated timber and its joints in corrosive environment are shown. This paper includes calculation results for dowel connections of wood structures using steel and carbon fibres cylindrical dowel pins in accordance with the applicable regulatory documents by means of finite element analysis in ANSYS software, as well as experimental findings.

Abstract: In this study, corrosion behavior of Incoloy 800 was studied in supercritical water containing sewage sludge and oxygen at various temperature from subcritical to supercritical environment. Surface and cross-section morphologies of the oxide films on Incoloy 800 was observed by scanning electron microscope. Corrosion will be obviously accelerated by increasing temperature. And the addition of oxygen in corrosion medium will cause the formation of various inorganic salts, forming a salt deposit layer on sample surface.

Abstract: Corrosion behavior of Incoloy 825 was studied in high temperature vapor with high concentration of NaCl. After 80 h exposure, a bi-layer structure was formed on sample surface after exposure. The outer layer is consisted of loose and large-grain oxides, and the inner layer is composed of fine-grain oxide. The whole layer was identified to be CrOOH/Fe₃O₄/Cr₂O₃/Incoloy 825 from outer to inner.

Abstract: In this study, magnetorheological elastomers (MREs) were synthesized using silicone rubber (SR) as the matrix element interspersed with 70 weight percent of corroded carbonyl iron particles (CIPs). The CIPs were corroded in dilute hydrochloric acid (HCl) for 4 hours. The rheological properties related to MR effect were experimentally examined in the absence and presence of magnetic field at various current using a rheometer. The experimental results depicted the MR effect of the MRE with corroded CIPs decreased one-half, 27% as compared to the non-corroded samples, 58%. The correlation between the purity of CIPs and storage modulus of MR elastomer is examined in this study.

Abstract: There have been two cathodic protection methods to inhibit corrosion of the structural steel piles which are being immerged under seawater, or to control corrosion of a hull part of the ship exposed to sea water. One of them is a sacrificial anode cathodic protection method that the steel pile can be protected with galvanic current by potential difference between sacrificial anode and corrosive structural steel. And, the sacrificial anode cathodic protection method have generally merits compared to impressed current method because it can be easily applied to everywhere which is not connected with electricity. However, when the steel piles are being submerged in low conductivity solution mixed with fresh water and sea water, the structural steel piles mentioned above have not been protected occasionally perfectively due to decreasing of galvanic current of zinc anode caused by deposited with oxide film on the surface of anode. In this study, four types of zinc anodes samples which are included with three types of additives such as NaCl, KCl, and ZnCl₂ were prepared, and galvanic currents, the polarization characteristics of these anodes was investigated using electrochemical methods such as polarization curves, impedance, cyclic voltammogtam and galvanic current in order to evaluate the effect of additive affecting to quality of zinc anode. The sample added with NaCl indicated the highest value of galvanic current density compared to other samples in the case of lower and higher conductivity solutions such as 0.32 and 2.97mS respectively, and the sample added with KCl revealed the smallest galvanic current density in middle value of conductivities such as 1.53 and 2.27 mS. Moreover, Zn sample no added with additive exhibited the smallest value of galvanic current density in the lowest conductivities such as 0.32 and 0.98 mS. Therefore, it is considered that the galvanic current of the sacrificial anode can be increased by adding of additive when the anode is submerged in low conductivity solution mixed with fresh water and sea water.

Abstract: Wear-resistant low alloy steels containing elements like Cr, Mo, attain their properties due to precipitation of carbides upon heat treatment. These steels are widely used for components in earthmoving and mining equipment. Even though the mechanical properties and wear behaviour of these steels are studied extensively, the studies on nature of carbide precipitation and their influence on corrosion behaviour are very rare. The present work attempts to correlate the microstructure with corrosion properties of low alloy wear resistant steel. After quenching from hot working temperature of about 900 °C, the alloy is subjected to tempering at two different temperatures i.e. 150 °C & 300 °C for durations of 1 h and 4 h. Two competitive process occur simultaneously effecting the hardness of the alloy during tempering i.e. (i) Softening due to transformation of martensite with depleting carbon (ii) Increase in hardness due to formation of carbide precipitates in the matrix. Transmission electron microscopy (TEM) of as quenched condition revealed fully martensite structure in the alloy. TEM investigation of 150 °C/ 4 h tempering condition, revealed presence of some amount of martensite and fine carbide precipitates in the alloy. TEM micrographs of 300 °C/ 4 h condition revealed relatively coarse carbides in a softer ferrite matrix. The presence of martensite and fine precipitates, resulted in relative improvements in wear and corrosion resistance respectively, for the alloy tempered at 150 °C for 4 h, when compared to the alloy tempered at 300 °C for 4 h.

Abstract: The problem in the large-scale industrialization for aluminum electrolysis is the corrosion resistance of cermet inert anodes in high temperature molten salts. In this paper, the ion structure of NiFe₂O₄-10NiO-based cermet anode composition in the electrolyte was investigated. The experiment results show that Al-F and Al-O-F complex ion structures are produced at room temperature and perhaps Me-F (Me=Ni, Cu, Fe), Me-O-F or Me-Al-O-F are also formed. Moreover, Al-F and Al-O-F ion structures exist from room temperature to 700 °C and from 1050 °C to 1200 °C; In the rearrangement and melting process of molten salt at 800 °C -1000 °C, the ionic structures are mainly Al-O-F ions; Me-F and Me-O-F ion structures were not found at high temperature, this indicates that Al in Al-O-F complex ion structures is partially replaced by Fe, Ni or Cu to form Me_xAl_aO_yF_z^{(z+2y-2x-3a)-}.

Abstract: The rust layer plays an important role in the corrosion of TRIP steels in marine environments. In this paper, salt spray tests were conducted in laboratory for the specimens after two-stage heat treatment. The results have shown that the corrosion performance of steel B is higher than that of steel A. The corrosion products in rust layer were a complex mixture of α-FeOOH, γ-FeOOH, Fe₃O₄ and γ-Fe₂O₃ after the salt spray tests. The contents of α-FeOOH in rust layer are more than those of γ-FeOOH in steel B. Steel B exhibits compact rust layers. This is attributed to the fact that alloying elements such as Ni, Cr, Cu and Mo can enrich at the rust layer/substrate interface. Therefore, the corrosion performance of steel B was improved.