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不鏽鋼杯子泡茶,危害健康嗎? Brewing Tea With Stainless Steel Mug – Is It Harmless To Our Health?

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Brewing Tea With Stainless Steel Mug – Is It Harmless To Our Health?

Does tea erode stainless steel mug and bring out chromium which is harmful to human health? This is a concern of office workers, who use insulated hydration bottle. Various stainless steel products have different functions in our daily life. But they are not necessarily undamageable. The wording 'stainless' means that it is relatively difficult to become rusty. Various products varied in their quality standard. This is for sure.

How to pick a stainless steel product?

Materials are the first criteria. Containers made of stainless steel grade 304 should be the first choice, for it comes with lower degree of chromium. Check the serial number printed on the stainless steel product, and opt for 18-8. The first figure indicates the level of chromium, and the second figure after the hyphen, nickel. More nickel indicates higher anti-rustiness.

Generally speaking, stainless steel products adhered to national standard actually release very minimal level of chromium. And we need not worry if it is harmful to our health.


Tea has very minimal acidity. Varied among the tea varieties and thickness of the tea, pH level of tea usually fluctuates between 5 to 7. Such low acidity means much lower erosion of stainless steel products.

Take a type of tea of pH 5.5 level for experiment. For the tea to soak in stainless steel mug and extract 0.4 milligramme of chromium, it would need approximately 246 hours. Which means continual soaking for ten days. And one has to make sure there is no passivation layer on the stainless steel product's surface. Also, the reaction has to be ongoing, before the soaking mug could bring out chromium.

Under normal condition, tea does not remain boiling temperature in stainless steel mug for 30 minutes. If we factor in passivation layer, the actual reaction is actually slower. Therefore, as long as we are using a stainless steel mug which is up to standard, and we are not keeping the tea for too long, we should not worry about excessive level of chromium. In fact, if we leave the tea in the stainless steel mug for several days, we should first worry about the mouldy and spoiled tea.

Health Tea Tips 保健

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