College】 【weak Ni-P electroless plating technology application in heat exchangers --- Power By 【China】 weak home network..

<br> Ni-P electroless plating technology in recent years developed advanced metal surface protection technology, is the use of electroless plating of metal or non-metallic surface to form a uniform layer of amorphous nickel-phosphorus metal coating, the base material and .the corrosive medium. isolated, the use of nickel-phosphorus corrosion resistance of metal coatings can achieve good anti-corrosion effect.. <BR> <BR> A technical brief <BR> <BR> plating by electroless plating solution .of the appropriate reducing agent to metal ions from the surface of metal catalyst and the reduction of the metal deposition process, also known as electroless. plating or autocatalytic plating.. The essence of plating chemical redox reactions, electron transfer, no external power supply of .the chemical deposition process.. Electroless nickel-phosphorus plating is the most representative one of the technologies.. <BR> <BR> Two nickel-phosphorus plating coating performance <BR> <BR> 2.1 <BR> < .; BR> corrosion resistance of Ni-P plating organized by the cellular composition of amorphous nickel-phosphorus alloy is homogeneous single-phase. system, there is no grain boundaries, dislocations and other defects and the chemical composition of tissue segregation, and will not .produce intergranular corrosion and stress corrosion, pitting resistance than the crystalline alloy good.. <BR> <BR> Ni-P plating coatings and coatings of phosphorus content, but also with coating porosity.. Phosphorus into phosphorus plating bath according to, .in phosphorus and high phosphorus plating bath.. Phosphorus content of phosphorus in the bath of 0.5% to 5%, the use of such solution is obtained by coating crystalline structure, high hardness, wear and corrosion characteristics of alkali.. P content of phosphorus .in the bath of 6% to 9%, the use of such solution available for the crystalline and amorphous coating Community, both corrosion and wear-resistant coating, the most widely used in industry.. High phosphorus content of phosphorus in the bath of 9 .% to 12%, the solution obtained by the use of such coating is amorphous, showing non-magnetic, is mainly used for coating the bottom of the computer hard drives and electronic equipment against electromagnetic interference shielding layer, the acidic. medium, good corrosion .resistance.. <BR> <BR> Amorphous nickel-phosphorus alloy coating is impregnated method, since the plating surface of the formation of catalytic reaction, no external current, free from the impact of power lines covered, avoid corners of the inherent .effects of electroplating.. Therefore, the plating of any complex shape, and any dip can be obtained where the same uniform coating thickness, coating porosity and low, so very good corrosion resistance.. <BR> <BR> 2.2 < .BR> <BR> wear resistance of a material under certain conditions, shown by the friction wear resistance, wear resistance and hardness are directly related.. Generally the higher the more wear-resistant material hardness, hardness of Ni-P plating is high ., up to 50HRC ~ 55HRC.. If after 300 ~ 400, ÑÉ heat treatment, hardness of Ni-P plating can be increased to 65HRC ~ 70HRC, it has good wear resistance.. <BR> <BR> Determination of the .corrosion resistance of three coatings <BR> <BR> (1) naphthenic acid corrosion of Ni-P plating environment at a temperature lower than 180, ÑÉ of naphthenic acid corrosion environment with good corrosion resistance.; at 180 ~ 300, ÑÉ .of naphthenic acid corrosion environment, the corrosion resistance decreased with increasing temperature; above 300, ÑÉ naphthenic acid corrosion environment, the metal plating Ni-P crystallization began, there intergranular corrosion, corrosion. performance dramatically.. <BR> <BR> .(2) sulfur, hydrogen sulfur corrosion of Ni-P plating environment in sulfur, hydrogen sulfur corrosive environment with good corrosion resistance, and the comparison of temperature changes of the school if the metal coating on the Ni-P .400 ~ 600, ÑÉ .in about 1h under the heat treatment, they can raise the metal coating at high temperature nickel-phosphorus sulfur, hydrogen sulfur corrosion resistance in corrosive environment.. <BR> <BR> (3) of ammonia water, hydrogen sulfide corrosion of .Ni-P plating environmental ammonia hydrogen sulfide in the corrosion resistance of the water corrosive environment better.. <BR> <BR> (4) water corrosion environment in the Ni-P plating is not corrosive environment of water chloride content in water ., has good corrosion resistance.. <BR> <BR> Four nickel-phosphorus plating technology <BR> <BR> from December 2000, our company has 13 in Southern Taiwan distillation unit using the heat exchanger tubes of nickel phosphorus .plating used in cold preservation. corrosive environment of water cooler tube bundle 5 55 months of continuous use coatings intact.. Used in low-temperature naphthenic acid environments 4 heat exchanger tubes were used continuously for 30 months and 23 months coatings intact.. Application in .high temperature naphthenic acid environment of the 4 heat exchanger tubes in the use of 23 months and 17 months respectively after the tube in the tube plate and the first part of local corrosion, tube coating intact.. <BR> <BR> Five .Corrosion and Improvement <BR> <BR> nickel-phosphorus plating equipment parts prone to corrosion mainly concentrated in the heat exchange tube head or tube sheet and other machining parts, tubes, and weld parts of the surface. depression and other parts, .these parts or sharp edges because of processes, resulting in partial coating porosity larger Ni-P plating for the potential higher than the potential of the tube, it is the site where the pore will produce electrochemical corrosion.. In addition, the operation grip part .of the construction of the damaged coating and surface coating corrosion damage caused by flawed is the main reason.. <BR> <BR>..