Stainless steel is in the air, water, acid, alkali, salt and other solutions, or other corrosive medium with a certain chemical stability of metal materials. When the composition of stainless steel contains a certain proportion of chromium and nickel composition, the corrosion resistance will be changed, that is, corrosion resistance, not easy to rust. 304 stainless steel material containing more than 18% chromium, as well as about 8% of nickel and molybdenum, titanium, silicon, aluminum and other trace elements. These elements have a high chemical stability, the steel surface will form a layer of oxide passivation film. The membrane is very thin and transparent, under a microscope to see, see the bright silver metal surface. This layer of passivation film to make stainless steel and the external media such as air, acidic liquid, such as isolation, to protect it from oxidation, enhance its corrosion resistance. Once the passive film is damaged, the chromium nickel and oxygen ions will be re generated passivation film, continue to play a protective role. Because of this self repair function, 304 stainless steel has a high corrosion resistance, it will never rust.
There are many grades of stainless steel. Common stainless steel models are 316#, 304#, 202#, 201#, etc., where 201# is stainless steel, 304# is to achieve the standard of food products of stainless steel, 316# is to reach the sea, the use of special anti-corrosion stainless steel. 304 stainless steel surface bright, high plasticity, good toughness, high mechanical strength, with welding, bending deformation characteristics. Corrosion resistance in acid and alkali gases, solutions and other media. Check 304 stainless steel true and false is a simple method: first, with concentrated brine to soak for 200 hours to see if there is a change; the second, with concentrated acid immersion for 10 hours to see if there is a change.
Non-magnetic (weak magnetic) stainless steel material belongs to single phase structure, easy to roll and no cracks. The magnetic (strong magnetic) stainless steel is a dual phase structure, which is not easy to roll and easy to crack. Therefore, it is not scientific to judge the quality of stainless steel with magnetism. The CF-8 standard 304# stainless steel with dual phase casting must be magnetic (usually micro magnetic), and its magnetic strength depends on the ratio of chromium and nickel.
The poor corrosion resistance of copper, copper rust will (commonly known as Pseudomonas). Lead elements of copper containing different proportions of the market, the so-called "free copper" faucet is actually "low lead content", and is not really "free". Copper is very harmful to human body, especially on children's intelligence development caused great negative impact. Strictly speaking, to achieve low lead or lead-free copper is very difficult. The customer is difficult to judge the quality of copper faucet, a lot of excess copper doped lead and zinc alloy material, its purpose is to reduce the production cost, but extremely harmful to human health.