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Pre-plating treatment of galvanized steel pipe

Dec. 04, 2019

Before galvanizing steel pipes, they must undergo pre-plating treatment:

Pickling, cleaning, rinsing, dipping solvent, and drying. The welded pipe is hoisted into the pickling tank for pickling (about 2 tons per hoist). About 26% hydrochloric acid solution is used for pickling. In order to prevent excessive pickling and acid mist volatilization, add 0.5 ~ 1.0g / L corrosion inhibitor and mist suppressant to the pickling solution. Pickling at room temperature is common. It is 30 to 60 minutes. In order to make the anti-corrosion steel pipes uniformly pickled, the steel pipe is hoisted 2 to 3 times by a crane during the pickling process to improve the pickling effect.

When the acid concentration drops to 100g / L, it should be replenished or replaced, and the iron content reaches 220 ~ 260g / L as waste acid discharge. The pickled steel pipe is hoisted to the washing tank for cleaning to remove the residual acid and iron salts accumulated on the surface of the steel pipe after pickling, and then hoisted to the washing platform and rinsed with 0.7 ~ 0.8Mpa of water. The steel pipe was suspended for dipping in a solvent tank. The dipping time was about one minute. The solvent was 600 ~ 650g / L zinc chloride, 80 ~ 100g / L ammonium chloride, and 1 ~ 2g / L OP-10 surfactant. In order to improve the effect of pre-plating in the solvent of steel pipes, the solvent always remains weakly alkaline, and then the crane is hoisted to the drying furnace rack to enter the drying furnace.

Optimization of sulfate galvanizing The biggest advantage of sulfate galvanized pipe is that the current efficiency is as high as 100% and the deposition rate is fast, which is unmatched by other galvanizing processes.

Optimization of sulfate galvanized pipe:

Because the crystallization of the coating is not detailed enough, the dispersing ability and the deep plating ability are poor, so it is only suitable for electroplating of pipes and wires with simple geometry. The sulfate electroplating zinc-iron alloy process optimizes the traditional sulfate zinc plating process. Only the main salt zinc sulfate is retained, and the remaining components are discarded. An appropriate amount of iron salt is added to the composition of the new process formula, so that the original single metal coating layer forms a zinc-iron alloy coating layer.

Galvanized Pipe

Galvanized Pipe

The reorganization of the process not only promotes the advantages of high current efficiency and fast deposition rate of the original process, but also greatly improves the dispersion and deep plating capabilities. In the past, complex parts could not be plated, now simple and complex parts can be plated, and the protective performance 3 to 5 times higher than single metals. Production practice proves that for continuous electroplating of wires and pipes, the grains of the coating are finer and brighter than the original, and the deposition rate is faster. The coating thickness meets the requirements within 2 to 3 minutes.

Galvanized steel pipes are divided into two types: hot-dip galvanizing and electro-galvanizing. The thickness of hot dipped galvanized steel pipe is thick, which has the advantages of uniform coating, strong adhesion and long service life. Electrogalvanized is low cost, the surface is not very smooth, and its corrosion resistance is much worse than that of hot-dip galvanized pipe.

In order to improve the corrosion resistance of steel pipes, general steel pipes are galvanized. Galvanized steel pipes are divided into two types: hot-dip galvanizing and electro-galvanizing. The thickness of hot-dip galvanizing is thick, the cost of electro-galvanizing is low, and the surface is not very smooth.