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Causes and solutions of leaky plating of hot-dip galvanized seamless pipe
Date:2020-07-14      Views:292Time      Label:Causes and solutions of leaky plating of hot-dip galvanized seamless pipe

1. The surface of the plated parts is not clean

(1) The surface of the plated parts contains paint, grease, and soldering; it can be polished or prepared with related solvents for scrubbing.

 

(2) Iron oxide; under pickling; continue pickling.

 

2. Pickling and operation

(1) Owing and over pickling. Under-pickling, leaving iron oxides (rust spots) on the surface of the plated parts; over-pickling, causing the surface structure of the steel substrate to be destroyed, the Si and a small amount of active metals contained in the steel substrate are attached to the surface of the plated parts, preventing iron and zinc Combination. Or due to over-pickling, the plated parts can absorb hydrogen. During zinc plating, hydrogen etc. expands due to heat to escape and miss plating.

Solution: Strictly control the pickling and grasp the pickling time.

 

(2) The plating parts are superimposed and accumulated during pickling, resulting in missed washing; or due to the structural reasons of the plating parts, there is no turning during pickling, which caused vortex gas and missed washing.

Solution: Extend pickling as much as possible and turn over frequently.

 

3. Assistant plating

(1) The concentration of additives is low, and the effect of plating is not ideal.

Solution: Adjust the appropriate concentration of additives.

 

(2) Improper proportion of additives and high zinc salt content make the salt film of the additives easy to absorb water and deliquesce, and the hydroxide decomposes into gas to explode zinc, which leads to leaky plating.

Solution: adjust the proportion of additives.

 

4. Zinc liquid composition and pot operation

(1) The aluminum content in the zinc solution is too high, resulting in missing plating;

Solution: Add zinc or use ammonium chloride to reduce aluminum content.

 

(2) The speed of the pan under the plating is too slow, the auxiliary will decompose and fail due to heat, resulting in missed plating. Adjust the speed of lower pot properly;

 

(3) The zinc immersion time is too short, so that the iron-zinc reaction can be carried out in the future;

 

(4) The zinc ash on the zinc liquid surface is not cleaned when the plated parts are put out of the pot, which makes the overheated zinc ash burning aid miss the plating;

 

(5) When the plated parts are put into the pan, due to the process hole or structure, when the high-temperature gas in the plated parts escapes due to heat, the additives will be burned to cause missing plating.

Solution: Sprinkle some ammonium chloride in an appropriate amount.

 

5. Plated material

(1) The surface of the steel contains refractory oxides of silicon and aluminum, which makes the iron-zinc reaction blocked.

 

(2) The steel matrix contains too much carbon, or too much iron carbide is produced during the refining process of the steel, which makes the combination of iron and zinc difficult, resulting in missed plating.

 

(3) Defects in the processing and forming of the plated material cause cracking of the material, and acid liquid, moisture and additives enter, resulting in missing plating. At present, there is no good solution except for the use of ammonium chloride.