Method of forming coating films and coated article
AssigneeNippon Paint Co., Ltd.
InventorsHiroyuki Sakamoto, Noriyuki Tsuboniwa, Motoki Fujii, Kazuo Morichika, Ichiro Kawakami
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Abstract
It is an object of the present invention to provide a method of forming a coating film by which a coating film excellent in weathering resistance, light degradation resistance, smoothness and the like can be formed on the outer panel portion of an article to be coated such as a car, and a coating film excellent in rust prevention can be formed on the inner panel portion (bag-structured portion) of the article to be coated, with the interface between the outer and inner panel portions of the article being excellent in rust prevention and finish as well, and by which resources saving and coating cost reduction can be expected.
Claims19
A method of forming a coating film
- which comprises, sequentially, process steps of applying an electrodeposition coating [1] to an article to be coated, a driving process step, and process steps of applying an electrodeposition coating [2] thereon, followed by a baking process step,
- wherein said process steps of applying the electrodeposition coating [1] comprise (i) a step of immersing the article to be coated in the electrodeposition coating and (ii) a step of applying a voltage between the article to be coated and the anode,
- said process steps of applying the electrodeposition coating [2] thereon comprise (i) a step of immersing the article to be coated in the electrodeposition coating, (ii) a step of applying a voltage higher than the voltage applied in step [1] (ii) between the article to be coated and the anode,
- said electrodeposition coating [1] containing a sulfonium group-containing resin,
- giving a film thickness to a face B of the article to be coated of not more than one tenth of the film thickness of a face A of the article when used in the electrodeposition coating of a coating with a resin solid matter of 20% by weight by a four sheet box method at 100 V and 40° C. for 120 seconds following a rise time of 5 seconds to provide the face A with a 20 to 30 μm film thickness, and
- said electrodeposition coating [2] having a time point at which the electric resistance value per unit volume of a deposited coat increases in the process of electrodeposition under a constant current condition.
Dependencies are inferred from the claim text.