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

When looking through the sales evaluations of other merchants on the e-commerce platform, the editor found the question "Is it normal for the inner liner of the stainless steel water cup to turn black?" "A lot of people asked the question, and then the editor carefully checked the replies from various merchants to this question. It was found that most merchants only answered that it was normal, but did not explain why it was normal, nor did they explain to consumers what caused the blackening.

Friends who own more thermos cups can open these water cups for comparison. Don't mind how long it has been used, just a simple comparison will find that different brands of water glasses have different light and dark effects inside the inner tank.Then we do the same when buying water bottles. Even the water cups of big brands will occasionally have different light and dark effects in the inner tank of the same batch of water cups. What is the reason for this?

Here I want to popularize the treatment process of the water cup liner with you. At present, the treatment of the stainless steel water cup liner is mainly based on these processes: electrolysis, sandblasting + electrolysis, and polishing. The principle of electrolysis can be searched on the Internet, and the editor will not state it again. To put it simply, through chemical reaction, the surface of the inner wall of the water cup is pickled and oxidized to achieve a smooth and smooth effect.

Because 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 surface of the inner wall by a machine or a manually controlled grinder.

Speaking of this, some friends have to ask again, which of these processes can control the sensitivity of the inner wall surface of the water cup? The effect after electrolysis can be bright, normal light and matte, which are mainly controlled by the electrolysis time and electrolysis chemical substances. Friends who have more water glasses in their hands can also observe that the inner wall of some water glasses is as bright as a mirror, which is called electrolytic brightness in the industry. The effect of sandblasting + electrolysis is frosted, but the fineness and brightness of the same frosting are also different. In contrast, some will appear brighter, while others will be completely matte, as if there is no refraction of light.

The same goes for polishing. There are many kinds 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 and the finer the wheel used, the final result is a mirror finish. However, 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.

The inner wall of the newly purchased thermos cup is dark and black to observe whether it is uniform. If it is not uniformly plaque-like, it cannot be judged that this water glass is normal. Maybe there is a problem with the material, or there may be a problem with the storage process. The sense of light and shade is consistent, and the color is uniform. There is no problem in using such a water cup.

Dongguan Zhanyi Commodity Technology Co., Ltd. specializes in the production of metal cups, plastic cups, coffee cups, suction mug, lunch boxes, food jar, travel mugs, portable water bottles, sports bottles, home life desktop trash cans, thermos bottles, etc.These products are all our annual exports, and are recognized and loved by the US, Europe, Australia, Japan, South Korea, Taiwan, Hong Kong and other consumers. Support for small quantity order, fast customization.