Is it normal for the inner tank of the stainless steel water cup to turn black?

When we looked through the sales reviews of other merchants on the e-commerce platform, we found that many people asked the question “Is it normal for the inner tank of the stainless steel water cup to turn black?” Then we carefully checked the responses from each merchant to this question and found that most merchants just The answer is normal, but it does not explain why it is normal, nor does it explain to consumers what causes the blackening.

Friends who own a lot of thermos cups can open these water cups and compare them. It doesn’t matter how long they have been used. Just a simple comparison will reveal that different water cups and different brands have different light and dark effects inside the liner. not exactly. The same goes for when we buy water cups. Even for big brand water cups, the inner liner of the same batch of water cups will occasionally show different light and dark effects. What causes this?

Here I would like to share with you the treatment process of the water cup liner. Currently, the main processes for processing the stainless steel water cup liner are: electrolysis, sandblasting + electrolysis, and polishing.

You can search the principle of electrolysis on the Internet, so I won’t elaborate on it. To put it simply, it is to pickle and oxidize the inner wall surface of the water cup through chemical reaction to achieve a smooth and smooth effect. Since the inside of the water cup is smooth and lacks texture if it is only electrolyzed, the manufacturer uses a sandblasting process to form very fine particles on the inner surface of the water cup to enhance the texture of the inner surface of the water cup.

Polishing is simpler than the electrolysis production process, but it is more difficult than electrolysis in terms of production difficulty. Polishing is performed on the inner wall surface by machine or manually controlled grinder. At this point, some friends want to ask again, which of these processes can control the sensitivity of the inner surface of the water cup?

The effect after electrolysis can be bright, normal bright or matte. This is mainly controlled by the electrolysis time and electrolytic chemical substances. Friends who have many water glasses can also observe that the inner wall of some water glasses is as bright as a mirror, which is very popular in the industry. The inner name is Jie Liang.

The effect of sandblasting + electrolysis is frosted, but the same frosted texture has different fineness and brightness. In comparison, some will appear brighter, while others will have a completely matte effect as if there is no light refraction. The same is true for polishing. There are many types of final polishing effects, which mainly depend on the fineness of the grinding wheel of the grinder used, and also on the length of polishing. The longer the polishing time, the finer the grinding wheel used, and ultimately the smoothness can be achieved. Mirror effect, but due to the difficulty of polishing control and high labor costs, the cost of electrolysis to achieve the same mirror effect is far lower than the cost of polishing.

If the inner wall of a newly purchased thermos cup is dark and black, you need to observe whether it is uniform. If it is not uniform and patchy, then you cannot judge that the water cup is normal. There may be a problem with the material, or it may be caused by the storage process. something is wrong. The light and dark feel are consistent, and the color is uniform. There is no problem in using this kind of water cup.