Development of an improved tube galvanizing process by prior metallic coating

• Novel method for tube galvanizing is established without using fluxing as an intermediate step.
• Fluxing process is successfully replaced by copper flash coating eliminating the process hazards associated with fluxing.
• Copper flash coating produces satisfactory coating after galvanizing in terms of microstructure, corrosion property and adherence.

Tube galvanizing is a very old and important process industrially. One of the significant process steps in tube galvanizing is the use of flux materials on cleaned tubes for temporary protection before dipping into the liquid zinc bath. However, the fluxing operation is somewhat hazardous and also causes zinc loss by dross and ash generation. An attempt has been made here for the first time to replace fluxing operation by applying a thin metal flash coating on clean tubes prior to galvanizing. The galvanized tubes are then characterized by SEM and EDS to find out the coating thickness and evolved phases. The galvanized tubes are subjected to corrosion tests and coating adhesion tests. The results are very encouraging confirming the presence of desired phases along with excellent corrosion resistance of these tubes.