Hot dip galvanizing is the traditional process of malleable iron pipe fittings
. It is not only a fundamental change in the plating method, but also a low cost, improved production environment and basically eliminated pollution. Because the malleable iron fittings
’ composition is complex and the structure is loose. There are many defects such as shrinkage holes, pores and blisters in the interior and surface of the roughcasts. At the same time, the surface is easy to form an iron oxide film, which makes the plating more difficult. and after the etching, carbon, silicon exposed to the surface, so that the overpotential of hydrogen is reduced, electroplating begins to deposit a large amount of hydrogen, the coating is difficult to deposit. Because of this, the various processes for electroplating zinc are only suitable for galvanizing of potassium (sodium) salts.
At present, the galvanizing of Malleable iron fittings is basically this process. The advantage of the potassium (sodium) salt-plated steel is that the coating is the production cost is significantly reduced. The disadvantage is that it is not easy to form a plating layer on the inner wall of the tube, the surface of the tube body is easy to change color, Affect the coating protection, iron impurities are a worries, and will not affect the normal production if it is not processed every month. The chloride bright zinc-iron-plated gold plating process, which was introduced in the early 1990s, maintained the protection performance of hot-dip plating and promoted the advantages of potassium (sodium) salt galvanizing to make up for the shortcomings of the process.
The strengths and weaknesses in the process reflect the new development of protective plating technology. Zinc-iron alloy is known as the ideal process to replace the galvanization of pipe fittings without pollution. From the development trend of surface treatment of malleable iron pipe fittings, hot-plating conversion to electroplating may be the future direction. It is inevitable that zinc-iron-plated gold replace malleable iron fittings galvanizing
are in the direction.