Abstract: A pretreatment apparatus for performing pretreatment before a painting process includes a treatment tank to be filled with a treatment liquid for degreasing and chemical conversion. A circuit section forms a circulation path for circulating the treatment liquid from the treatment tank to the treatment tank. A purifying section removes dust, chemical sludge and oil from the treatment liquid circulated to the treatment tank through the circulation path.

Abstract: A pretreatment apparatus for performing pretreatment before a painting process includes a treatment tank to be filled with a treatment liquid for degreasing and chemical conversion. A circuit section forms a circulation path for circulating the treatment liquid from the treatment tank to the treatment tank. A purifying section removes dust, chemical sludge and oil from the treatment liquid circulated to the treatment tank through the circulation path.

Abstract: A composite paint for an automotive outer panel comprises an electrodeposition paint film coated on the surface of a steel sheet. The electrodeposition paint film has a minimum melt viscosity not less than 0.2 during hardening and consists essentially of a water paint composition in an amount ranging from 50 to 85 parts by weight upon conversion to a solid content, and a partially cross-linked resin in an amount ranging from 15 to 50 parts by weight upon conversion to a solid content. Additionally, an intermediate paint film is coated on the electrodeposition paint film and has a hardening starting time ranging from 15 to 20 minutes.

Abstract: A composite paint film coating formed on a steel sheet of an automotive vehicle body. The composite paint film coating is comprised of an electrodeposition paint film (I) coated on the steel sheet, and an intermediate paint film (II) coated on the first paint film. The electrodeposition paint film has a minimum melt viscosity not less than 0.2 during hardening. The electrodepositon paint film is formed of cathodic electrodeposition paint composition which includes a cationic thermosetting resin (1), and an already cross-linked particulate resin (2). The particlate resin is an addition-polymer formed between a fist compound (A) having at least two primary amino groups in a molecule, and a second compound (B) having at least two .alpha.,.beta.-ethylenic unsaturated groups. The particulate resin has an average particle size ranging from 0.01 to 1 .mu.m. The weight ratio ((2)/(1)) in solid content between the particulate resin (2) cationic thermosetting resin (1) is within a range from 0.03 to 0.15.

Abstract: A paint film arrangement formed on an outer panel of an automotive vehicle. The paint film arrangement comprises a film of an electrodeposition paint formed on the surface of a steel plate of the automotive vehicle outer panel. The surface of the electrodeposition paint film has a center line average height Ra within a range of 0.3.mu..ltoreq.Ra.ltoreq.0.8.mu.. The total of values of power spectrum of the surface of the electrodeposition paint film is not more than 80 .mu.V.sup.2 within a wavelength range not more than 0.5 mm. Additionally, a film of an intermediate coat paint is formed on the surface of the electrodeposition paint film. The intermediate coat paint has a hardening starting time ranging from 15 to 20 minutes. The hardening starting time is determined according to a logarithmic decrement of the intermediate coat paint by an oscillated pendulum type viscoelasticity measuring device.

Abstract: A composite paint film formed on a steel sheet of an automotive vehicle body. The composite paint film comprises an electrodeposition paint film (I) coated on the steel sheet, and an intermediate coat paint film (II) coated on the first paint film. The electrodeposition paint film is formed of an epoxy-based cationic electrodeposition paint composition and has a minimum melt viscosity not less than 0.2 during hardening. The epoxy-based cationic electrodeposition paint composition includes an amine-added epoxy resin (1) of the type which may be hardened with a blocked isocyanate, a colloidal silica-containing gelled particulate (2), and an alkyltin ester compound of a liquid aliphatic carboxylic acid. The above-mentioned colloidal silica-containing gelled particulate is formed by dispersing a mixture of an acrylic copolymer having a hydrolizable alkoxysilane group and a cationic group and a cationic acidic colloidal silica in water to carry out a cross-linking reaction in particles of the colloidal silica.

Abstract: In making a peripheral joint between first and second metal panels such as, e.g., outer and inner panels of an automobile door by hemming the first panel after application of a rust preventive sealant, the sealant is used in a quantity in excess of just sufficiency for completely filling in gaps in the joint to ensure that the excess portion of the sealant is pressed out of the joint by the end of the hemming operation, and the press die member used in the hemming working is formed with a groove in its hemming surface such that the sealant pressed out of the joint is confined within a space defined by the groove and shaped in conformance with the shape of the groove so as to serve as an external seal which closely covers the edge of the hemmed marginal part of the first panel.