Electrodeposition coating method and electrodeposition coating apparatus

An electrodeposition coating method, comprising:

• a degreasing/cleaning step of removing dirt or an oil and fat content on a surface of a target object to be coated;
• a chemical conversion step, performed after the degreasing/cleaning step, of forming a chemical conversion layer on the surface of the target object from which the dirt or the oil and fat content has been removed;
• and
• an electrodeposition coating layer formation step, performed after the chemical conversion step, of forming an electrodeposition coating layer including a first electrodeposition coating film and a second electrodeposition coating film stacked on the first electrodeposition coating film on the surface of the target object on which the chemical conversion layer has been formed, wherein
• the degreasing/cleaning step includes a degreasing step of degreasing and cleaning the target object, from the surface of which the dirt or the oil and fat content has not been removed yet, through ultrasonically vibrating a degreasing solution which is stored in a degreasing tank and in which the target object is immersed, using an ultrasonic vibrator provided on a wall portion of the degreasing tank, and
• the electrodeposition coating layer formation step includes:
• a first electrodeposition step of forming, in a first electrodeposition tank, the first electrodeposition coating film on the target object through application of a direct current voltage between the target object on which the chemical conversion layer has been formed and a first counter electrode;
• a first rinsing step of rinsing, after the first electrodeposition step, the target object on which the first electrodeposition coating film has been formed with rinse water;
• a rinse water removal/reduction step of removing or reducing, after the first rinsing step, the rinse water remaining on a rinse water stagnating surface of the target object that has been rinsed, the rinse water stagnating surface being substantially horizontal and thus stagnating the rinse water thereon;
• warm air blowing step of blowing warm air on the target object after the rinse water removal/reduction step such that, on the target object having gone through the removal or reduction of the rinse water on the rinse water stagnating surface, the first electrodeposition coating film formed on a portion of the target object near the first counter electrode has a higher electrical resistance than the first electrodeposition coating film formed on a portion of the target object far from the first counter electrode;
• and
• a second electrodeposition step of forming, in a second electrodeposition tank after the warm air blowing step, the second electrodeposition coating film on the target object on which the warm air has blown, through application of a direct current voltage between the target object and a second counter electrode.