Talking about the Influence of Sealant on the Galvanized Layer of Steel Barrel

Talking about the Influence of Sealant on the Galvanized Layer of Steel Barrel

Jiangsu Baoying County Metal Products Factory Qiao Ping

In recent years, in order to meet the requirements of petrochemical product packaging, China's steel drum products, in terms of specifications and varieties, are constantly developing and increasing. Among the 200 liter steel drum products, galvanized barrels account for a large proportion. At present, there are no special standards for galvanized steel drums. The barrel industry basically refers to the GB325-84 standard, and its effect is good.

GB325-84 "200L closed steel drum" stipulates: the barrel body and the top of the barrel and the bottom of the barrel are double-hemed. The gaps in the layer must be filled with seals. The sealant is made of heat-resistant, cold-resistant and solvent-resistant materials with good performance and compatibility with the contents.

In the past, the steel drum industry has been using brown sugar bone glue as a sealant. The glue has poor compactness and environmental adaptability. After the 1980s, sealant samples were imported from abroad. After digestion and absorption, China's new sealing glue has been developed and applied. At present, brown sugar bone glue has been basically replaced. However, during use, the sealant has different effects on the galvanized layer of the steel drum. I have done it with three representative types of sealants. The following tests:

First, the test group

Group 1: WS-type water-based sealant produced by Chemical Industry Chemical Plant of Xi'an Jiaotong University.

Group 2: 812 steel barrel crimp sealing packing produced by Tianjin Steel Barrel Sealing Packing Factory. During the test, it was dissolved in a warm water bath.

Group 3: Sealant for the Egret brand steel drum produced by Kaiyuan Latex Factory in Xiamen, Fujian.

Two: Test method:

Three test methods are used for each group:

1. Put a quantitative amount of sealant in a closed container, place it in a galvanized sheet, and hang the galvanized sheet in the space of the closed container to observe the change.

2. Place a galvanized sheet on the other side of the sealant that has just been applied over the other side of the sealant and observe the change.

3. Apply one side of the sealant and one uncoated galvanized sheet. After the gel is dried and solidified, put it into a closed container and observe the change.

Third, the test results

The test results are as follows:

experiment method
Group
Group 1
2 teams
3 groups
First
6 days
No change
5 days
Type 2
5 days
No change
4 days
Third
No change
No change
No change

Note: The number of days in the table refers to the number of days required to produce white powder on the surface of the sample.

After testing, the PH values ​​of groups 1, 2, and 3 were 10, 7, and 120, respectively, and the groups 1 and 3 were alkaline. Groups 1 and 3 contain about 5% ammonia water. Because the chemical properties of ammonia are extremely unstable, it is easy to decompose, volatilize, and release ammonia gas, so the glue has an irritating ammonia smell.

Fourth, the cause analysis:

The production of galvanized steel drums is generally made of semi-finished products made of thin steel sheets, then galvanized, and finally assembled for sealing. At present, cyanide galvanizing, ammonium salt galvanizing, potassium salt galvanizing and the like are commonly used. The entire plating process is generally pre-plating, electroplating and post-plating. In the post-plating treatment process, a passivation process is used to form a passivation film whose main component is chromate on the surface of the galvanized layer to protect the stability of the zinc layer. Since the sealant contains ammonia, the passivation film is destroyed by chemical reaction with the blunt film during volatilization. The zinc in the galvanized layer also directly reacts with the oxygen in the air to form white zinc powder, which also destroys the galvanized layer, thereby reducing the corrosion resistance of the galvanized layer and affecting the galvanized steel drum. Use performance.

V. Conclusion

The third test method showed that the sealant coating did not react with the galvanized layer after drying. In order to take advantage of the filling, matching and stability of the sealant, to avoid the influence of the galvanized layer, a reasonable sizing method must be selected. After spraying (brushing) the glue, it needs to be dried at room temperature for 6-8 hours before being wound. If the automatic spraying process is carried out on the sealing machine, the residual ammonia must be volatilized before screwing on the barrel stopper to ensure the quality of the galvanized steel drum.

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