Free electrons in the conductor in the direction of movement to form a current. If the direction and magnitude of the current is always the same, so that the current is called DC. For example, the battery and battery output current is DC. If the magnitude and direction of the current change with time is called the AC. Such as industrial and lighting electricity is AC. The intensity and
direction of alternating current in each country or region vary with time. China's industrial and civil power are alternating current, voltage 220V, frequency of 50 times per second. Of course, DC is not all smooth DC, if the direction of the current is always the same and the size is constantly changing, just like a person's pulse, called pulse DC.
In the
electroplating process, metal products connected to the negative power supply,
the positively charged metal ions are reduced to metal crystals on the negative
electrode to form a plating layer. The coating thickens with the continuation
of the process, on the anode, the process is the opposite of the cathode, the
metal atoms will be handed over to become ions into the plating solution. If
the use of alternating current, while the negative parts, electroplating, while
the anode, and the plating solution to dissolved metals, cannot get complete and
useful coating, so usually only with direct current plating and not with
alternating current. Of course, with the progress of electroplating technology,
can be used with pulsed DC to achieve some improvement on the coating, but the
cathodic process is still in the mainstream of the role of DC
electrode position. Because some plating species in the presence of certain
exchange factors (with a negative half-cycle of the pulse), the crystallization
will be more refined. Some plating such as chrome plating, requires a
completely smooth DC.
