A complete analysis of the painting process of shaft couplings: key steps to improve durability and aesthetics
As the core components of mechanical transmission systems, cardan shaft couplings are widely used in metallurgy, mining, shipbuilding and heavy machinery. The painting process is not only related to the appearance, but also directly affects the anti-rust performance and service life. This article will introduce the painting requirements of cardan shaft couplings in detail, including surface treatment, coating selection, spraying process and quality control, to help users optimize the painting process and improve product performance.
1. Surface treatment before painting (key foundation)
(1) Thorough cleaning Remove oil stains: Use industrial cleaning agents (such as acetone or special degreasers) to remove oil stains, dust and rust on the surface of the coupling.
Sandblasting/shot blasting: Sandblast or shot blast the metal surface to ensure that the roughness is controlled within Ra3.2μm~6.3μm to enhance the adhesion of the paint film.
(2) Check surface defects The welding parts need to be polished smooth to remove burrs, welding slag and other protrusions.
If cracks or pores are found, they need to be repaired and re-polished first, otherwise the coating will easily peel off after painting.
2. Coating selection and painting process
Spraying thickness: usually 50-80μm, even coverage is required to avoid missing spraying or excessive thickness causing sagging.
(2) Topcoat spraying Recommended topcoat: polyurethane topcoat (strong weather resistance) or alkyd enamel (economical and practical).
Color standard: usually orange-red (JB/T standard), but can be customized according to customer needs8.
Spraying distance: keep the spray gun 15-20cm away from the workpiece to avoid paint accumulation due to being too close or uneven paint film due to being too far away.
(3) Treatment of special parts Flange end face and spline part: only apply anti-rust grease to avoid spraying affecting assembly accuracy.
Bearing hole and cross shaft contact surface: need to be protected with tape to prevent paint mist from entering and affecting lubrication performance.
3. Paint quality control (1) Paint film thickness detection Use a coating thickness gauge to ensure that the total thickness of the primer + topcoat is between 120-150μm.
(2) Adhesion test Use the cross-cut method (ISO 2409 standard). The paint film should not fall off or peel off in a large area.
(3) Drying and curing Natural drying: more than 24 hours at room temperature.
Bake curing (optional): bake at 60-80℃ for 2-4 hours to accelerate curing and increase the hardness of the paint film.














