تحقیق روی رفتار خوردگی اتصالات لحیم کاری مس

Investigation on Corrosion Behaviour of Copper Brazed Joints 

تحقیق روی رفتار خوردگی اتصالات لحیم کاری مس

ABSTRACT

DHP (Deoxidized High Phosphorus(copper is widely used in various heat transfer units such as, air conditioners, refrigerators, evaporators and condensers. Copper sheets and tubes (ISODHP) were brazed with two different brazing alloys. Corrosion resistances of the joints were examined by polarization test. The selected fillers consisted of a silver-based brazing alloys (hard solder); AWS-BCu5, and a copper-based filler AWS BCuP2. All the joints were brazed utilizing two different brazing processes including furnace brazing under argon and air atmosphere. All of the fillers were used with and without flux. The microstructure of the brazed sheets was examined using both optical and scanning electron microscope (SEM). Hardness and leak tests were carried out on all the brazed tubes. In all brazing alloys selective and galvanic corrosion were observed in filler metals, but in copper phosphor alloys the copper adjacent to the joints were noticeably corroded by pitting method. It was found that the samples brazed with BAg5 filler metal using argon furnace show a higher resistance to corrosion. They also have a good ductility in the brazed zone.

 

بنزوتریازول: یک ممانعت کننده مؤثر خوردگی برای آلیاژهای مس

Benzotriazole:An effective corrosion inhibitorfor copper alloys 
بنزوتریازول: یک ممانعت کننده مؤثر خوردگی برای آلیاژهای مس

ABSTRACT

Copper is the only engineering metal that is noble metal. It resists many corrosive environments. But copper tarnish or corrodes under some circumstances. In recent years, investigators have shown that a system of tarnish or corrosion control for copper, brass and bronze can be built around the organic compound, 1, 2, 3, benzotriazole. Benzotriazole forms a strongly bonded chemisorbed two-dimensional barrier fi lm less than 50 angstroms thick. This insoluble fi lm, which may be a monomolecular layer, protects copper and its alloys in aqueous media, various atmospheres, lubricants, and hydraulic fl uids. Benzotriazole also forms insoluble precipitates with copper ions in solution (that is, it chelates these ion), thereby preventing the corrosion of aluminum and steel in other parts of a water system.
J. B. Cotton. Imperial Metal Industries Ltd., Birmingham, England, has studied the tarnishing of copper and copper alloys exposed to humid environments, and the possibility of the prevention of staining by reaction with triazole type compounds. At the Second International Congress on Metal Corrosion, New York, 1963, he summarized the properties of commercially available benzotriazole and the reaction of this class of compound with copper ions. His report, “Control of Surface Reaction on Copper by Means of Organic Reagents”, points out that the nitrogen-hydrogen group, and at least one of the other nitrogens in the ring, is involved in the complex bonding arrangements to copper. The polymeric chains or monomolecular plate-like complexes completely cover a clean metal surface, affording excellent protection. In the more typical case, benzotriazole probably plugs holes and defects in the copper oxide surfaces fi lm. Use of benzotriazole, and other protective chemicals such as tolutriazole, constitutes a signifi cant advance in the quest for corrosion inhibitors. It demonstrates that effective inhibition can function through the formation of true chemicalbonds.