There are many reasons for blackening the surface of the electric heating element:
1, first of all, it may be reason that the electric heating element itself has been burned, so the surface will be black. If this is the case, you should pay attention and do not continue to use this product.
2. It may be caused by abnormal power supply or frequent power failure. The electric heating pipe in use will appear black because of repeated power failure or abnormal power supply.
3.May be the controller contact point poor contact, power cord plug and electric socket poor contact caused.
4.Energized heating oxidation phenomenon, electric heating element energized heating after a period of time, due to the influence of air or humid environment, the surface will produce some black objects because of oxidation, like burning stainless steel with a candle flame, the surface will form a layer of black material. This situation is relatively common, and the black oxide is non-toxic, and the electric heating tube can continue to be used.
