Pub Date : 2002-12-01DOI: 10.1179/000705902225006651
M. Zhou, J. Zhang, D. Shu, K. Li, H. Ni, W. Y. Zhang, B. Sun, J. Wang
Abstract A study has been conducted of the resistance to corrosion in molten zinc of borophosphate enamels. The melting temperature of the enamels was adjusted by adding the carbonates of alkali metals and alkaline earth metals. Scanning electron microscopy was used to examine solidified interfaces between the enamels and the molten zinc. At low magnification (× 30) no evidence of components from the B2O3-P2O5 enamels was detected by electron probe in the industrially pure zinc near the interface with the enamel, but elemental Zn was found in the initially zinc free B2O3-P2O5 enamels. When the interface was examined at a magnification of 1000 times, it was confirmed by electron probe that no phosphorus from the borophosphate enamel was present in the zinc matrix at a position 60 μm from the interface. The results show that the borophosphate enamels are extremely resistant to corrosion in molten zinc.
{"title":"Corrosion resistance of borophosphate enamels in molten zinc","authors":"M. Zhou, J. Zhang, D. Shu, K. Li, H. Ni, W. Y. Zhang, B. Sun, J. Wang","doi":"10.1179/000705902225006651","DOIUrl":"https://doi.org/10.1179/000705902225006651","url":null,"abstract":"Abstract A study has been conducted of the resistance to corrosion in molten zinc of borophosphate enamels. The melting temperature of the enamels was adjusted by adding the carbonates of alkali metals and alkaline earth metals. Scanning electron microscopy was used to examine solidified interfaces between the enamels and the molten zinc. At low magnification (× 30) no evidence of components from the B2O3-P2O5 enamels was detected by electron probe in the industrially pure zinc near the interface with the enamel, but elemental Zn was found in the initially zinc free B2O3-P2O5 enamels. When the interface was examined at a magnification of 1000 times, it was confirmed by electron probe that no phosphorus from the borophosphate enamel was present in the zinc matrix at a position 60 μm from the interface. The results show that the borophosphate enamels are extremely resistant to corrosion in molten zinc.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"13 1","pages":"289 - 292"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81540409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006714
M. Schneider, H. Pohl
Abstract The aluminium alloy AA 6013 is of increasing significance with regard to the aircraft industry. In addition to its mechanical properties, corrosion resistance, especially against local corrosion phenomena (i.e. pitting corrosion and crevice corrosion), is very important in structural applications. In this work, the authors present the use of electrochemical noise analysis (ENA) in combination with a corrosion cell design, which was developed for the investigation of crevice corrosion. It is shown that ENA is a very useful technique for the early detection of crevice corrosion processes in the earliest stages of attack.
{"title":"Crevice corrosion investigation on AA 6013: application of electrochemical noise analysis","authors":"M. Schneider, H. Pohl","doi":"10.1179/000705902225006714","DOIUrl":"https://doi.org/10.1179/000705902225006714","url":null,"abstract":"Abstract The aluminium alloy AA 6013 is of increasing significance with regard to the aircraft industry. In addition to its mechanical properties, corrosion resistance, especially against local corrosion phenomena (i.e. pitting corrosion and crevice corrosion), is very important in structural applications. In this work, the authors present the use of electrochemical noise analysis (ENA) in combination with a corrosion cell design, which was developed for the investigation of crevice corrosion. It is shown that ENA is a very useful technique for the early detection of crevice corrosion processes in the earliest stages of attack.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"8 1","pages":"298 - 304"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89838242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006688
A. E. El Warraky, A. E. El Meleigy
Abstract The synergistic inhibition of aluminium bronze corrosion by 4-phenyl semicarbazide hydrochloride (PSC) and the iodide ion in HCl of pH (1·8-2) at 60°C has been assessed by polarisation studies, Tafel plots, X-ray photoelectron spectroscopy and Auger electron spectroscopy. The addition of 0·01M KI to 0·01M PSC improved the inhibition efficiency from 86 to 94% owing to the formation of a CuI-PSC complex which is more compact, protective and hard than the film formed in the absence of iodide. The inner layer of this protective film contains a small amount of aluminium oxide, which increases the protective nature of the film and retards the dissolution of the underlying aluminium bronze.
通过极化研究、塔菲尔图、x射线光电子能谱和俄歇能谱，研究了60℃时4-氨基苯脲盐酸盐(PSC)和盐酸中碘离子对铝青铜腐蚀的协同抑制作用。0.01 m KI对0.01 m PSC的缓蚀率从86%提高到94%，这是由于与无碘化物时形成的膜相比，形成的CuI-PSC配合物更致密、保护性更强、硬度更高。这种保护膜的内层含有少量的氧化铝，这增加了膜的保护性质，并延缓了下面的铝青铜的溶解。
{"title":"Electrochemical and spectroscopic investigation of synergestic effects in corrosion inhibition of aluminium bronze Part 1 – In pure HCl","authors":"A. E. El Warraky, A. E. El Meleigy","doi":"10.1179/000705902225006688","DOIUrl":"https://doi.org/10.1179/000705902225006688","url":null,"abstract":"Abstract The synergistic inhibition of aluminium bronze corrosion by 4-phenyl semicarbazide hydrochloride (PSC) and the iodide ion in HCl of pH (1·8-2) at 60°C has been assessed by polarisation studies, Tafel plots, X-ray photoelectron spectroscopy and Auger electron spectroscopy. The addition of 0·01M KI to 0·01M PSC improved the inhibition efficiency from 86 to 94% owing to the formation of a CuI-PSC complex which is more compact, protective and hard than the film formed in the absence of iodide. The inner layer of this protective film contains a small amount of aluminium oxide, which increases the protective nature of the film and retards the dissolution of the underlying aluminium bronze.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"119 1","pages":"305 - 310"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79044243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006697
J. Sullivan, D. Worsley
Abstract An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m-2, and Z alutite 55 wt-%Al, 0·67 g m-2). Organically coated steels show relatively little zinc runoff (< 0·25 g m-2) indicating their effectiveness in preventing surface corrosion. Runoff levels measured do not exceed permissible levels of zinc for drinking water and the measured zinc runoff levels pose little threat to organisms if leached into soil. Using an accelerated laboratory test in which distilled water is sprayed onto specimen panels in a recirculatory system for 100 h a good correlation can be obtained with external exposure for up to 6 months exposure. For 12 months exposure iron zinc intermetallic galvanising (galvanneal) begins to become covered in a protective oxide layer, which cannot form under the conditions of the accelerated test. Despite this, the fit for most specimen types is excellent. Where the predictive test fails is when the galvanising layer is breached revealing an efficient iron cathode site. This occurs first for electrocoated zinc after 16 months exposure. Similar predictive results can be obtained using a scanning vibrating electrode technique (SVET) in a semiquantitative manner and an immersion electrolyte of 0·1 wt-%NaCl. Again the predictions are initially very accurate but following 12 months exposure the fit for specimens of electrozinc is poor due to the breaching of the galvanising layer.
在工业/海洋塔尔博特港风化场进行了一项调查，以评估16个月来各种镀锌材料的锌径流。在16个月的暴露中，裸锌和电锌的锌径流水平最高(4.38和4.20 g m-2)，其次是普通镀锌钢基体，即热浸镀锌(HDG)钢(0.15 wt-%Al) (2.87 g m-2)和铁锌金属间镀锌钢(镀锌，2.36 g m-2)。镀锌(IZ)具有比HDG更高的初始径流速率，这是因为涂层中存在铁/锌金属间化合物，促进了锌的阳极溶解。HDG具有更稳定的径流速率，在7-8个月后，由于IZ表面腐蚀产物的积累，其径流速率超过IZ。铝/锌合金涂层钢的径流率比一般镀锌材料低得多，因为结构中的铝提供了一层强大的保护性氧化屏障涂层，提高了耐腐蚀性(Galfan 5 wt-%Al, 2.04 g - m2, Z alalite 55 wt-%Al, 0.67 g - m2)。有机涂层钢表现出相对较少的锌径流(< 0.25 g m-2)，表明它们在防止表面腐蚀方面的有效性。测量到的径流水平没有超过饮用水锌的允许水平，测量到的锌径流水平如果渗入土壤，对生物的威胁很小。使用加速实验室试验，在循环系统中将蒸馏水喷洒到样品板上100小时，可以获得与外部暴露长达6个月的良好相关性。暴露12个月后，铁锌金属间镀锌(galvanneal)开始被氧化保护层覆盖，在加速试验条件下不能形成氧化保护层。尽管如此，适合大多数标本类型是非常好的。预测测试失败的地方是当镀锌层被破坏，露出一个有效的铁阴极位置。这种情况首先发生在接触16个月后的电镀锌上。半定量的扫描振动电极技术(SVET)和0.1 wt-%NaCl的浸没电解质也可以得到类似的预测结果。同样，预测最初是非常准确的，但在暴露12个月后，由于镀锌层的破坏，电锌样品的适合性很差。
{"title":"Zinc runoff from galvanised steel materials exposed in industrial/marine environment","authors":"J. Sullivan, D. Worsley","doi":"10.1179/000705902225006697","DOIUrl":"https://doi.org/10.1179/000705902225006697","url":null,"abstract":"Abstract An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m-2, and Z alutite 55 wt-%Al, 0·67 g m-2). Organically coated steels show relatively little zinc runoff (< 0·25 g m-2) indicating their effectiveness in preventing surface corrosion. Runoff levels measured do not exceed permissible levels of zinc for drinking water and the measured zinc runoff levels pose little threat to organisms if leached into soil. Using an accelerated laboratory test in which distilled water is sprayed onto specimen panels in a recirculatory system for 100 h a good correlation can be obtained with external exposure for up to 6 months exposure. For 12 months exposure iron zinc intermetallic galvanising (galvanneal) begins to become covered in a protective oxide layer, which cannot form under the conditions of the accelerated test. Despite this, the fit for most specimen types is excellent. Where the predictive test fails is when the galvanising layer is breached revealing an efficient iron cathode site. This occurs first for electrocoated zinc after 16 months exposure. Similar predictive results can be obtained using a scanning vibrating electrode technique (SVET) in a semiquantitative manner and an immersion electrolyte of 0·1 wt-%NaCl. Again the predictions are initially very accurate but following 12 months exposure the fit for specimens of electrozinc is poor due to the breaching of the galvanising layer.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"102 1","pages":"282 - 288"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88946743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006633
R. Venkatesan, M. Venkatasamy, T. Bhaskaran, E. Dwarakadasa, M. Ravindran
Abstract The deep sea corrosion of ferrous alloys that undergo uniform corrosion without forming a passive layer is related to the amount of dissolved ox ygen available in the sea water. The performance of some ferrous alloys at depths of 500, 1200, 3500, and 5100 m in the Indian Ocean has been studied. The results of atomic absorption spectroscopy have revealed that the corrosion product present on mild steel coupons is FeOOH. The results of experiments in shallow water have shown that micro- and macrobiological growths play a significant role in the corrosion of ferrous materials. However, in deeper waters, the absence of macrofouling was evident, and corrosion was not related to any biological product but mainly to the electrochemical reaction of these alloys with sea water. The results of morphological studies by SEM on the surfaces of ex posed specimens are also presented.
{"title":"Corrosion of ferrous alloys in deep sea environments","authors":"R. Venkatesan, M. Venkatasamy, T. Bhaskaran, E. Dwarakadasa, M. Ravindran","doi":"10.1179/000705902225006633","DOIUrl":"https://doi.org/10.1179/000705902225006633","url":null,"abstract":"Abstract The deep sea corrosion of ferrous alloys that undergo uniform corrosion without forming a passive layer is related to the amount of dissolved ox ygen available in the sea water. The performance of some ferrous alloys at depths of 500, 1200, 3500, and 5100 m in the Indian Ocean has been studied. The results of atomic absorption spectroscopy have revealed that the corrosion product present on mild steel coupons is FeOOH. The results of experiments in shallow water have shown that micro- and macrobiological growths play a significant role in the corrosion of ferrous materials. However, in deeper waters, the absence of macrofouling was evident, and corrosion was not related to any biological product but mainly to the electrochemical reaction of these alloys with sea water. The results of morphological studies by SEM on the surfaces of ex posed specimens are also presented.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"148 1","pages":"257 - 266"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88993997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006705
G. Carbajal De la Torre, R. Nava Mendoza, M. Espinosa-Medina, A. Martínez-Villafañe, J. González-Rodríguez, V. Castaño
Abstract Potentiodynamic polarisation curves have been used to evaluate the corrosion performance of 1008 carbon steel coated with hybrid (inorganic-organic) and mixed oxide coating systems deposited by dip coating. Several coatings have been prepared by the sol-gel method, using metallic alkox ides, such as tetraethylorthosilicate, aluminium isopropoxide, and zirconium propoxide, and polymers like allyl methacrylate (AMA) and polymethylmethacrylate (PMMA), together with zirconium dioxide (ZrO2) and silicon and aluminium oxides (SiO3-Al2O3). The aqueous test solutions included hydrochloric acid (HCl), sodium chloride (NaCl), and sulphuric acid (H 2SO4) at various concentrations (0·1, 0·5, and 1M). Scanning electron microscopy was used to examine the coatings following testing. The results have shown that SiO2-Al2O3 based coatings are not beneficial for corrosion protection in HCl, but are of value in the other aqueous media. In 1·0M HCl, the best protection was offered by a hybrid SiO2-ZrO2-poly(methylmethacrylate-allyl methacrylate) (P(MMA-AMA)) coating. In NaCl, the best results, were generally obtained with SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. Similarly, in H2SO4, the best results were generally displayed by the SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. The corrosion behaviour of the coatings is discussed in terms of the integrity and stability of the film.
摘要采用动电位极化曲线对1008碳钢进行了浸镀复合(无机-有机)涂层和混合氧化物涂层的腐蚀性能评价。用溶胶-凝胶法制备了几种涂层，使用金属醛化物，如四乙基硅酸盐、异丙酸铝和丙酸锆，以及聚合物，如甲基丙烯酸烯丙酯(AMA)和聚甲基丙烯酸甲酯(PMMA)，以及二氧化锆(ZrO2)和硅铝氧化物(sio2 - al2o3)。水溶液包括不同浓度(0.1、0.5和1M)的盐酸(HCl)、氯化钠(NaCl)和硫酸(h2so4)。测试后用扫描电子显微镜检查涂层。结果表明，SiO2-Al2O3基涂层在HCl介质中没有良好的防腐效果，但在其他水溶液介质中有良好的防腐效果。在1.0 m HCl条件下，混合sio2 - zro2 -聚甲基丙烯酸甲酯-甲基丙烯酸烯丙酯(P(MMA-AMA))涂层的保护效果最好。在NaCl条件下，SiO2-Al2O3和SiO2-ZrO2-P(MMA-AMA)涂层效果最好。同样，在H2SO4中，SiO2-Al2O3和SiO2-ZrO2-P(MMA-AMA)涂层通常表现出最好的效果。从膜的完整性和稳定性两方面讨论了涂层的腐蚀行为。
{"title":"Corrosion protection of 1008 carbon steel by hybrid coatings","authors":"G. Carbajal De la Torre, R. Nava Mendoza, M. Espinosa-Medina, A. Martínez-Villafañe, J. González-Rodríguez, V. Castaño","doi":"10.1179/000705902225006705","DOIUrl":"https://doi.org/10.1179/000705902225006705","url":null,"abstract":"Abstract Potentiodynamic polarisation curves have been used to evaluate the corrosion performance of 1008 carbon steel coated with hybrid (inorganic-organic) and mixed oxide coating systems deposited by dip coating. Several coatings have been prepared by the sol-gel method, using metallic alkox ides, such as tetraethylorthosilicate, aluminium isopropoxide, and zirconium propoxide, and polymers like allyl methacrylate (AMA) and polymethylmethacrylate (PMMA), together with zirconium dioxide (ZrO2) and silicon and aluminium oxides (SiO3-Al2O3). The aqueous test solutions included hydrochloric acid (HCl), sodium chloride (NaCl), and sulphuric acid (H 2SO4) at various concentrations (0·1, 0·5, and 1M). Scanning electron microscopy was used to examine the coatings following testing. The results have shown that SiO2-Al2O3 based coatings are not beneficial for corrosion protection in HCl, but are of value in the other aqueous media. In 1·0M HCl, the best protection was offered by a hybrid SiO2-ZrO2-poly(methylmethacrylate-allyl methacrylate) (P(MMA-AMA)) coating. In NaCl, the best results, were generally obtained with SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. Similarly, in H2SO4, the best results were generally displayed by the SiO2-Al2O3 and SiO2-ZrO2-P(MMA-AMA) coatings. The corrosion behaviour of the coatings is discussed in terms of the integrity and stability of the film.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"13 1","pages":"293 - 297"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77506481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006624
N. Rajendran, G. Latha, S. Rajeswari
Abstract Potentiodynamic anodic polarisation measurements have been carried out on type 316L stainless steel (as a reference material) and on alloys 33 and 24 in a simulated flue gas desulphurisation environment in order to assess the localised corrosion resistance. The results showed that the pitting corrosion resistance was higher in the case of alloys 33 and 24 than in the reference material owing to the higher contents of nitrogen, chromium, and molybdenum. An accelerated leaching study conducted on the alloys 33 and 24 showed only minor tendencies for the leaching of metal ions at various impressed potentials. Observations by SEM confirmed the lower tendency towards pitting of the alloys 33 and 24.
{"title":"Localised corrosion behaviour of alloys 33 and 24 in simulated flue gas desulphurisation environment","authors":"N. Rajendran, G. Latha, S. Rajeswari","doi":"10.1179/000705902225006624","DOIUrl":"https://doi.org/10.1179/000705902225006624","url":null,"abstract":"Abstract Potentiodynamic anodic polarisation measurements have been carried out on type 316L stainless steel (as a reference material) and on alloys 33 and 24 in a simulated flue gas desulphurisation environment in order to assess the localised corrosion resistance. The results showed that the pitting corrosion resistance was higher in the case of alloys 33 and 24 than in the reference material owing to the higher contents of nitrogen, chromium, and molybdenum. An accelerated leaching study conducted on the alloys 33 and 24 showed only minor tendencies for the leaching of metal ions at various impressed potentials. Observations by SEM confirmed the lower tendency towards pitting of the alloys 33 and 24.","PeriodicalId":9349,"journal":{"name":"British Corrosion Journal","volume":"484 1","pages":"276 - 281"},"PeriodicalIF":0.0,"publicationDate":"2002-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76373339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-12-01DOI: 10.1179/000705902225006660
D. Agarwal
Abstract The test results from an earlier investigation by the author on the mechanical behaviour of a low nickel nickel-copper alloy exposed to a solution of 3·5%NaCl + 10%MgCl2 with and without ammonia indicated that the presence of 1% ammonia alters the failure mode and affects the load bearing capacity of the material. In the present investigation, further tests have been conducted on the same alloy to study its mechanical/corrosion behaviour on exposure to an aqueous solution of ammonia in comparison with exposure to a similar solution of ammonia containing 3·5%NaCl + 10%MgCl2. A constant displacement rate of 9·6 × 10-3 μ m s-1 was used and the concentration of ammonia was maintained at 5%. On exposure to the 5% aqueous ammonia solution, the mechanical properties of the alloy were degraded significantly and the material exhibited a brittle stress corrosion type of failure. However, on exposure to 5% ammonia in the presence of 3·5%NaCl + 10%MgCl2, there was less change in failure mode relative to that in air and a significant improvement in the mechanical properties of the material compared with those in aqueous ammonia. This indicates that the presence of MgCl2 and/or NaCl can be beneficial when low nickel copper alloys are exposed to ammonia. This paper presents the experimental results and observations from the recent tests, and discusses the relative roles of ammonia and NaCl/MgCl2 in determining the mechanical properties and modes of failure in a low nickel content copper-nickel alloy.
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Pub Date : 2002-12-01DOI: 10.1179/000705902225006679
A. Zaky, F. Assaf, S. S. Abd El Rehim, B. M. Mohamed
Abstract The electrochemical behaviour of two copper-nickel alloys in solutions containing the carbonate ion has been investigated by cyclic voltammetric, potentiodynamic, and current/time transient techniques. Among the variables studied were alloy composition, stepwise increasing potential, scan rate, carbonate ion concentration and temperature. The composition of the compounds formed on the alloy surface during the anodic polarisation was characterised using X-ray diffraction analysis. The dissolution behaviour of the alloy consists of two potential regions separated by the critical potential Ecrit. The first potential region involves the selective dissolution of the more active constituent, nickel, and the appearance of one anodic peak A1 as a result of the formation of Ni(OH)2on the alloy surface. The second potential region relates to the simultaneous dissolution of copper and nickel. This region was characterised by the appearance of four anodic peaks A2, A3, A4, and A5, which are related to the formation of Cu2O, {CuO and Cu(OH)2}, CuCO3-Cu(OH)2 composite, and NiOOH, respectively. Potentiostatic current/time transients showed that the formation of Ni(OH)2, Cu2O, CuO, Cu(OH)2, CuCO3-Cu(OH)2 and NiOOH layers involves a nucleation and growth mechanism under diffusion control.
采用循环伏安法、动电位法和电流/时间瞬态技术研究了两种铜镍合金在含碳酸盐离子溶液中的电化学行为。研究的变量包括合金成分、逐级递增电位、扫描速率、碳酸盐离子浓度和温度。利用x射线衍射分析表征了阳极极化过程中合金表面形成的化合物的组成。合金的溶解行为由两个由临界电位Ecrit隔开的电位区组成。第一个电位区涉及更活跃的成分镍的选择性溶解，以及由于在合金表面形成Ni(OH)2而出现的一个阳极峰A1。第二个电位区与铜和镍的同时溶解有关。该区域出现了四个阳极峰A2、A3、A4和A5，它们分别与Cu2O、{CuO and Cu(OH)2}、CuCO3-Cu(OH)2复合物和NiOOH的形成有关。恒电位电流/时间瞬变表明，Ni(OH)2、Cu2O、CuO、Cu(OH)2、CuCO3-Cu(OH)2和NiOOH层的形成涉及扩散控制下的成核和生长机制。
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