The corrosion processes of the galvanized steel changed differently under 3.5wt% NaCl and chloride-free SRL solutions. Fig.7 shows the SEM images in different sampling time intervals. Fig.7 (a) presented the SEM images of the as-received sample of galvanized steel before the tests. This images presented here were for comparison with those of corroded samples. Evidently, the zinc coatings were compact, smooth and completely covered the substrate surface, no corrosion was found before the immersion on the electrodes surface; loose corrosion products absorbed on the electrode surface under both of the chloride-free and 3.5wt% NaCl SRL solutions after 1 days (Fig. 7(b)); when the time elapsing, pitting corrosion occurred obviously on the galvanized steel after 14 days (Fig.7 (c)) under the SRL solution containing 3.5wt% NaCl, and non-uniform corrosion occurred on the galvanized steel after removing the rust layer. These results were consistent with that of the EIS results as shown in Fig.4 and further supported the assumption of the oxygen diffusion control step. With time, the rust layer absorbed on the electrode was gradually damaged under the erosion of Cl - . However, lots of needle-like rust layer was adherent and compactly absorbed on the electrode surface under chloride-free SRL solution, the color of the surface became murky gray and little pitting corrosion was found on the zinc coating after removing the rust layer (Fig.7 (d)).
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Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an eﬀective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern ﬁtting of the measured spectra. All the rust is composed mainly of goethite, akagane´ite, lepidocrocite and magnetite. Among these iron oxides, akagane´ite in particular is the major component in the rust. Additionally, the amount of akagane´ite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akagane´ite is generally considered to facilitate the corrosion of steel, but our results indicate that akagane´ite in the rust of Fe-Ni alloy is quantitatively diﬀerent from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akagane´ite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentiﬁed chloride is related to the corrosion rate of steel.
The transformation mechanism of the rust layer induced by pyridine derivatives can be attributed to the fact that the N atoms and O atoms in the three pyridine derivative molecules have strong electronegativity ; in addition, the carboxyl [40-41], hydroxyl  and amino  groups can be adsorbed onto the surface of the rust layer through the coordination between the N or O atoms and the ferric ion. Otherwise, the outermost layers of N and O atoms both contain an unpaired electron; however, the coordination ability of the O atom to Fe ions is stronger than that of the N atom because the outer electrons of the O atoms are not saturated, and it can provide a plurality of the lowest energy space track . Thus, one can deduce that the smoother rust surface treated by 2-picolinicacid and 2- hydroxypyridine compared to that treated by 2-aminopyridine can be ascribed to the stronger coordination ability of the O atom.
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The XAFS measurements using synchrotron radiation X- rays were carried out at BL27B of the Photon Factory in the Institute of Materials Structure Science of the High Energy Accelerator Research Organization in Tsukuba, Japan. The XAFS spectrum of pure goethite around the Fe K absorption edge was taken in the transmission mode. That of the rust layer around the Cr K edge was taken in the ﬂuorescence mode. Figure 2 shows the schematic drawing of the XAFS measurement system in the transmission mode. The synchro- tron radiation with a white spectrum from a bending magnet was monochromatized by a Si(111) double-crystal mono- chromator. To eliminate the higher harmonics, the mono- chromator was detuned so that the intensity of the mono- chromatized beam was 40% of maximum at each absorption edge. In the transmission mode, the intensities of photons incident on the sample and passing through it were detected in two ionization chambers: one 5 cm in length ﬁlled with ﬂowing nitrogen gas and the other 31 cm in length with a mixed gas of 50% nitrogen and 50% argon. A 7-element germanium detector was used to detect the intensities of ﬂuorescent X-rays from the sample, which are proportional to the number of photons absorbed by target elements, in the ﬂuorescence mode. Energy calibration was based on the well- known absorption edge of 5.989 keV for metallic Cr and that of 7.113 keV for metallic Fe.
was applied in 1996, using X-ray diﬀraction at SPring-8 synchrotron radiation facility. It was shown that the formation of -FeOOH was promoted and/or crystal growth of -FeOOH was suppressed by the surface treatment. The increase in the protective ability index (PAI) of the rust layer indicates that the protective goethite was predominantly formed under the eﬀect of the surface treatment. In conclusion, it can be said that the surface treatment worked well to promote the formation of the protective goethite rust layer on the weathering steel bridge during the 10- year exposure. [doi:10.2320/matertrans.48.579]
Nyquist plots for the specimens in acidchloride solution (200 ppm Cl ¹ , pH 4) at various immersion intervals under OCP are presented in Fig. 4. The impedance spectra of the steels showed a very small semicircle in the higher frequency region and a large semicircle in the lower frequency region, indicating the formation of a rust layer on the steel surface. This two-time constant behavior is caused by the reaction between the specimen and electrolyte and simultaneously between the rust layer and electrolyte. Based on the above impedance spectrum features, the physical model and equivalent circuit for ﬁ tting the EIS data are presented in Fig. 5. 2426) The circuit consists of the following elements: a solution resistance, R s , two constant
The study of the rust layer formed on steel and its control lead to an improvement in the performance of steel. A rust layer formed on a low-alloy steel surface is generally able to impede the penetration of corrosives from an atmosphere. This ability of the so-called ‘protective’ rust layer enables the atmospheric corrosion resistance of the steel. It is well- known that weathering steel, which contains small amounts of Cr, P and Cu, possesses high atmospheric corrosion resistance because of the strong protective ability of the rust layer formed on the steel for impeding the penetration of corrosives.
Temperature variations relating to the Regular surface, Rust Layer and CRM for each shot are shown in figure 8. There is no significant distinction as observed in the signal intensity investigation. Under the same experimental conditions, the rust layer showed the highest mean temperature value over 10 shots. The results in table 1 validate the experimental accuracy of LIBS for single shot interrogation because of the accuracy errors (not greater than 1.1 %). The calculated plasma temperature relies strongly on the slope of the Boltzmann plots and thus, temperature accuracy is also dependent on the standard error of the slope. Values of intercept in Boltzmann plots are rarely used to validate the accuracy of the measured plasma temperature. To ensure some sort of reliability of using temperature measurements to characterise the rust sample using LIBS, approximations must be adopted to define the plasma state.
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immersion tests in the synthetic seawater, as shown in Fig. 5. In rust layer, the epoxy and corrosion product are co-existed: black area is epoxy and grey area is corrosion product. The specimens without Mo and with 0.05 mass% Mo and 0.1 mass% Mo had considerably porous rust layer on the steel surface. Whereas comparatively dense rust layer was ob- served on the specimen with 0.2 mass% Mo, as shown in Fig. 5(d), which means that the homogeneity of the rust layer was greater than that of other steels. These results support EIS results, indicating that 0.2 mass% Mo steel had the lower depression angle. The 0.2 mass% Mo steel can be expected to improve corrosion resistance due to the formation of nonpo- rous and protective rust layer on the surface.
A rust layer on a steel surface is generally considered to be responsible for protection of the steel against corrosives in atmospheric environment. It is well known that the rust layer, so called ‘‘protective’’ rust layer, formed on a weathering steel which contains a small amount of Cr, P and Cu has strong protective ability for atmospheric corrosion of the steel due to its densely packed microstructure and cation selectivity. 1) In the last decade, it has been elucidated that the inner stable and protective rust layer which covered the surface of a weathering steel for more than a quarter of a century mainly consists of nano-particles of Cr-goethite, -FeOOH phase containing Cr. 2) Most recently, X-ray
From Figure 3 and Figure 4, the outer rust in 30 days was flaky, and cluster distribution in some local part. The main composition was γ-FeOOH and with a small amount of α-FeOOH. The flaky rust was γ-FeOOH. The inner rust layer was bent flaky and evenly distribute relatively, the main ingredient was Fe 3 C with a small amount of Fe 3 O 4 , γ-FeOOH and β-FeOOH. The outer rust in 90 days
The results of IRS and XRD together indicated that a large amount of -FeOOH existed in the rust layer, which is closely related to the abundant Cl − in the “three highs” atmosphere of the south sea. However, the foreign elements Ca and Mg were not detected in the corrosion products, which might be in the form of free ions in the rust layer. According to the protective ability index (PAI) in a previous study , the value of the mass ratio “" was very small in this study, around 0.2, indicating that the rust layer had no protective effect with the increasing time.
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The results of Dong et. al.  show that the pitting potential decreased as the exposure time extended, and were explained as being covered with a rust layer. The difference between current research and Dong et. al.’s is that the rust layer of current research is alien substance, while Dong et. al.’s is formed during corrosion. The acceleration of rust layer on pitting corrosion is confirmed by these researches. It is obvious from here that the adherence of alien rust on stainless steel facilitates the initiation of localized corrosion.
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Fig. 8 shows the micromorphology of the cross section of the rust layer on carbon steel and low alloy steel. In all corrosion stages, the rust formed on carbon steel was only one layer that was rougher and more porous than that on the nickel-containing steel surface. The more porous structure of the rust layer led to a less effective barrier against the ingress of precipitation and chloride pollutants and a higher corrosion rate, and the results coincide with the corrosion kinetics curves very well. The poor adhesion and crack-richness of the rust layer led to bubbling, flaking and mass loss.
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The relative difference in the speciﬁc surface area of SOL and SIL can be inferred from the presence of a considerable amount of akaganeite (¢-FeOOH) which has a tunnel structure and contributes to a high surface area and with large pore size. The enrichment of Ni and Cr inﬂuences the reduction of particle size in the rust and its structure and compostion. 8,36 39) The SA above 50 m 2 /g has small pores always ﬁlled with water by the adsorption and capillary condensation. Further, it prevents the transfer of corrosive agents into the pore thus leading to the high protective nature of weathering steels to atmospheric corrosion. 37) From the above results, it is clear that the SIL has a higher surface area, which contributes to the protective ability of rust layer from atmospheric pollutants.
using a combination of peptide mass fingerprinting (PMF) and MSMS fragmentation. Most of the identi- fied proteins corresponded to enzymes belonging to photosynthesis, metabolism, biosynthesis, binding and defence response, whose behaviour pattern was different in relation to susceptibility/resistance of the studied genotypes and to the BTH/BABA induction to pathogen response. Results obtained in this work suggested that plants could reduce their photosyn- thesis and other energy metabolism and enhance the production of defence-related proteins to cope with the stress. On the other side, we postulated that resistance induced by the chemicals operates via different mechanisms: BABA inducer could act via phenolic biosynthesis pathway, whereas resistance provided by BTH inducer seems to be mediated by defence and stress-related proteins. These results provide a step to understand the molecular basis of the induced resistance to rust in pea. Nevertheless, a higher collection of candidates will be essential to elucidate target key elements involved in SAR response using integrated studies.
Reactions of registered winter wheat cultivars to 8 leaf rust isolates are listed in Table 5. Of 19 cul- tivars only the cultivar Bona Dea was resistant to all rust isolates like NIL possessing Lr19 . Most cultivars were resistant at least to one leaf rust isolate. Out of 19 tested winter wheat cultivars only 3 cultivars Pinta, Questor and Mv Palotas were susceptible to all rust isolates. Cultivars Viglanka, Karolinum, Bertold, Petrana and Rapsodia dis- played similar reactions resembling those of NIL possessing Lr26. Another group of cultivars with mutually similar reaction pattern comprised cul- tivars Apache, Median, Ezopus, Karpatia, Alacris. Reactions of cultivars Bodyček and Mulan were Table 5. Reactions of selected winter wheat cultivars to eight different leaf rust isolates and results of the molecular marker analysis
The genotype WK 2278 produced (5549 kg -1 ha) grain yield followed by WK 2408 (4404 kg -1 ha), Wk 2355 (4402 kg -1 ha), WK 2214 (4206 kg -1ha ) and WK 2438 (4187 kg -1ha ). However, the genotypes which were free from stripe rust with good yield could be the future variety of mid hills of Nepal (Table 1). Some genotypes showed less or free from leaf rust could be the future variety where leaf rust prevails. The genotype WK 2278, WK 2438 and WK 2352 showed no ACI for both rust and it was a high yielder among the tested genotypes. The WK 2214 also gave good yield (4206 kg -1 ha) even the ACI of leaf rust 57.5 and it could be a good vriety in hills where stripe rust prevails. The losses in yield due to stripe rust varied 4.2-68.8 per cent depending on the resistance of variety. Maximum yield reduction of 68.3 per cent was observed in old cultivar (Madhu et al., 2012). But in case of leaf rust loss was found less than the stripe rust.
In the present investigation also ICGV 86699 is highly resistant to rust showed much longer (> 25 days) incubation period as compared to earlier report (12.33 days) by Dwivedi et al.,(2001). The possible causes of this variation are the pathogen population, variation in temperature and humidity. All these can substantially influence components of resistance, particularly incubation period, sporulation index and leaf area damage. Mehan et al., (1994), who reported >60 % leaf area damage and Liao et al., (1990) reported 82-83 per cent leaf area damage. It is noteworthy that the susceptible check TMV 2 showed much greater leaf area damage (>98 %) in present study. The fact that components of rust resistance are not fully complementary is highlighted by several recombinants, recombinant line number 4 had more incubation period 20 days and more numbers pustules (21.50) and leaf area damage 2.5 per cent and 1.5 per cent ruptured pustules in F 6 population.
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Abstract: The demand for cowpea (Vigna unguiculata L. Walp) is higher than supply in Ghana due to low yields caused by pathogenic diseases, predominantly rust disease. The use of rust resistant cultivars is the most effective method to control cowpea rust. Genetic variations among cowpea genotypes may be potential sources of rust resistance to control cowpea rust and increase cowpea yield and production in Ghana. The study assessed rust disease incidence and severity among cowpea genotypes and determined resistance to cowpea rust under field conditions. Twenty-four cowpea genotypes were sowed in four agro-ecological zones in two cropping seasons in Ghana. Cowpea rust incidence, severity, area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) were significantly (p < 0.05) higher in the semi-deciduous forest and minor cropping season compared with deciduous forest, coastal savannah, Sudan savannah and major cropping season. The cowpea genotypes also showed significant differences (p < 0.05) in response to rust infection. Positive and negative correlations existed in rust incidence, severity, AUDPC and rAUDPC within the agro-ecological zones and cropping seasons. The differences observed were due to variations in climatic conditions and genetic composition of the cowpea genotypes. Five cowpea genotypes were better slow rusting, eleven cowpea genotypes were slow rusting and eight cowpea genotypes were fast rusting. Interestingly, eleven cowpea genotypes showed resistance and eight cowpea genotypes showed moderate resistance to cowpea rust. The rust resistant cowpea genotypes identified in this work can be recommended for farmers to cultivate and used in breeding programmes to further improve the crop. This will maximize yields and increase cowpea production particularly in rust prone areas.