The surface of the newly made stainless steel electric heating tube is bright and light, but the surface of the electric heating tube will be darkened after a period of heating. Many customers worry about whether the electric heating tube is broken, or not. Now, let's explain how the surface of the electric heating tube will turn black after heating for a period of time.
There are two situations in which the electric heating tube becomes black after a period of time:
Oxidation caused by electric heating:
After heating for a period of time, due to the influence of air or wet environment, the surface of the electric heating tube will produce some black objects due to oxidation. It will produce a black substance on the surface of the stainless steel when it burns stainless steel with candle. This is a common case, and the black oxide is nontoxic and the electric heating tube can continue to be used.
The burning phenomenon caused by high temperature:
Another possibility is that the electric heating tube is burned by burning the surface of the tube because of the high temperature. The electric heating pipe will not be used at this time.
So when the surface blackening of electric heating tube heating after a period of time, we have to determine what causes it. If it has a resistance value, it can work to show that it is only caused by oxidation; if there is no resistance value, it should be burnt out.
In the use of electric heaters, a black substance appears on its surface due to the influence of air and environment, which requires the use of blackening. Blackening is actually a process of heat treatment of stainless steel and other metal objects. After treatment, there will be a layer of oxide film to achieve the purpose of corrosion protection and rust prevention. After heat treatment, it will improve the wear resistance of the heater surface, improve the surface hardness, and do not affect the components in the electric heater.
Under conventional working conditions, the simplest way to blacken the surface of electric heaters is the following steps:
First, clean the metal tube surface and keep it clean.
Two is the surface degreasing treatment, this process can be completely placed in the metal tube in the degreasing solution. The pH value of the degreasing solution is best at about 13, and the time is not less than half an hour. Rinse with clean water after degreasing.
Then the acid washing can be carried out, the pH value of the acid washing liquid is about 3, the treatment time is not longer than 10 minutes, and the clean water is cleaned after the acid washing.
Blackening treatment: the pH value of the pool solution is 2-4, the treatment time is 10 minutes up and down, and after the blackening, it is incomparably cleaned.
Finally dry, oil;