Considering aviation and space sectors, aluminium alloys are commonly used due to its excellent mechanical and physical properties. Though satellite hard-ware is confined to controlled environment, it requires anticor...Considering aviation and space sectors, aluminium alloys are commonly used due to its excellent mechanical and physical properties. Though satellite hard-ware is confined to controlled environment, it requires anticorrosive treatment over metal substrate followed by a systematic coating scheme. The trivalent chromium coating was deposited over three aluminium alloys namely AA6063, AA7075 and AA6082. The variation in corrosion resistance property of trivalent chromium over each aluminium alloy has been studied in detail. The Neutral Salt Spray (NSS) test result shows that trivalent chromium coating over AA7075 alloy is affected by pitting corrosion compared to other two alloys. In addition to that, NSS test also proves that thickness of the layer does not have any influence corrosion resistance property of trivalent chromium coating. Furthermore, ions in trivalent chromium coating was identified using Secondary Neutral Mass Spectroscopy (SNMS) and degradation of coating in a corrosive liquid studied using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) instrument to understand mechanism of corrosion. The results indicated that both coating and substrate is involved in corrosion process. The number of elements dissolved in to salt solution reveals the weak ionic bonding of coating towards substrates. In comparison, AA7075 alloy has weaker bonding than AA6082 and AA6063 series. The alloying elements such as zinc and copper are removed from substrate by corrosive solution.展开更多
A new chromium-free conversion film was obtained on surface of a ZnAl alloy by chemical conversion process. Influence of the additives in treating solution containing cerium salt on the corrosion protection of the con...A new chromium-free conversion film was obtained on surface of a ZnAl alloy by chemical conversion process. Influence of the additives in treating solution containing cerium salt on the corrosion protection of the conversion film formed on zinc alloy was investigated. Corrosion tests and electrochemical measurements in sodium chloride solution were performed . The microstructure and composition of the coatings were examined by means of SEM, EDS and XRD. It was found that the corrosion protection capabilities of the conversion film are markedly increased with the cerium nitride plus additives (hydrogen fluoride acid and an organic inhibitor) treating process. The modified conversion film is an organic/inorganic composite coating and is much more corrosion resistant than the conventional chromate conversion coating and the single cerium conversion coating.展开更多
Cr(VI) is a widespread environmental contaminant and a known human carcinogen. Biosorption is a very common method to remove toxic Cr(VI) from industrial waste water. In biosorption Cr(VI) is reduced to less toxic Cr(...Cr(VI) is a widespread environmental contaminant and a known human carcinogen. Biosorption is a very common method to remove toxic Cr(VI) from industrial waste water. In biosorption Cr(VI) is reduced to less toxic Cr(III) and adsorbed in biosorbent as Cr(III). Effective biosorbents contain hydroxy groups;it may be aliphatic or aromatic. Kinetics of reduction of Cr(VI) by an aromatic alcohol, benzyl alcohol, (which is an important volatile component of flowers of some night blooming plants) in micellar media have been studied spectrophotometrically. Micellar media is a probe to establish the mechanistic paths of reduction of Cr(VI) to Cr(III). Effects of electrolytes are studied to support the proposed reaction mechanism. Suitable surfactant & suitable concentration of electrolyte enhance the biosorption property.展开更多
文摘Considering aviation and space sectors, aluminium alloys are commonly used due to its excellent mechanical and physical properties. Though satellite hard-ware is confined to controlled environment, it requires anticorrosive treatment over metal substrate followed by a systematic coating scheme. The trivalent chromium coating was deposited over three aluminium alloys namely AA6063, AA7075 and AA6082. The variation in corrosion resistance property of trivalent chromium over each aluminium alloy has been studied in detail. The Neutral Salt Spray (NSS) test result shows that trivalent chromium coating over AA7075 alloy is affected by pitting corrosion compared to other two alloys. In addition to that, NSS test also proves that thickness of the layer does not have any influence corrosion resistance property of trivalent chromium coating. Furthermore, ions in trivalent chromium coating was identified using Secondary Neutral Mass Spectroscopy (SNMS) and degradation of coating in a corrosive liquid studied using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) instrument to understand mechanism of corrosion. The results indicated that both coating and substrate is involved in corrosion process. The number of elements dissolved in to salt solution reveals the weak ionic bonding of coating towards substrates. In comparison, AA7075 alloy has weaker bonding than AA6082 and AA6063 series. The alloying elements such as zinc and copper are removed from substrate by corrosive solution.
文摘A new chromium-free conversion film was obtained on surface of a ZnAl alloy by chemical conversion process. Influence of the additives in treating solution containing cerium salt on the corrosion protection of the conversion film formed on zinc alloy was investigated. Corrosion tests and electrochemical measurements in sodium chloride solution were performed . The microstructure and composition of the coatings were examined by means of SEM, EDS and XRD. It was found that the corrosion protection capabilities of the conversion film are markedly increased with the cerium nitride plus additives (hydrogen fluoride acid and an organic inhibitor) treating process. The modified conversion film is an organic/inorganic composite coating and is much more corrosion resistant than the conventional chromate conversion coating and the single cerium conversion coating.
文摘Cr(VI) is a widespread environmental contaminant and a known human carcinogen. Biosorption is a very common method to remove toxic Cr(VI) from industrial waste water. In biosorption Cr(VI) is reduced to less toxic Cr(III) and adsorbed in biosorbent as Cr(III). Effective biosorbents contain hydroxy groups;it may be aliphatic or aromatic. Kinetics of reduction of Cr(VI) by an aromatic alcohol, benzyl alcohol, (which is an important volatile component of flowers of some night blooming plants) in micellar media have been studied spectrophotometrically. Micellar media is a probe to establish the mechanistic paths of reduction of Cr(VI) to Cr(III). Effects of electrolytes are studied to support the proposed reaction mechanism. Suitable surfactant & suitable concentration of electrolyte enhance the biosorption property.
