Primerless process (3C1B/3-Wet) and compact painting

The traditional "electrophoresis + primer surfacer + basecoat + clearcoat" process requires multiple baking cycles. The primer-surfacer-free process blends the primer surfacer into other layers, completing it in a single pass.

In a nutshell: Primer-surfer = omitting the independent primer coat and applying wet-on-wet continuously, significantly saving energy and reducing consumption but demanding more of equipment and cycle time.

I. Conventional vs. Primerless (middle-coat-free)

Traditional 3C2B is "primer surfacer + basecoat + clearcoat" each baked once; primer-surfacer-free (3C1B/3-Wet) combines the functions of basecoat and primer surfacer, applying wet-on-wet continuously and then baking once, eliminating one baking cycle.

II. Provincial-level Logic

• Function merging: High-solid color paint combines filling and coloring.
• Wet-on-wet: No baking between coats, continuous spraying.
• One-time drying: Saves one round of drying room energy consumption.

III. Energy Conservation and Requirements

Saving baking means saving energy consumption and cycle time, and also reducing VOC treatment load. But it places higher demands on coating stability, robot spraying accuracy, and oven temperature control.

Note: The primerless process has higher requirements for substrate flatness. If sheet metal and electrophoretic quality are not up to standard, omitting the primer will expose defects.

Summary

The primerless (3C1B/3-Wet) process integrates primer functions into the basecoat, applies coats wet-on-wet consecutively, and cures them in a single bake, eliminating one baking cycle to save energy, reduce consumption, and lower VOC load, but it demands higher coating stability, spray accuracy, and substrate flatness.

Frequently Asked Questions (FAQ)

What is the primerless process?

It is a compact process in vehicle painting that omits the independent primer coat, integrating the filling and adhesion functions of the primer into the basecoat, which is sprayed wet-on-wet continuously and then baked once, also known as 3C1B/3-Wet.

How does the primerless process save energy?

The traditional primer requires a separate baking pass; the primerless process combines this step, eliminating one baking cycle means less energy consumption and cycle time, and also reduces the VOC treatment load.

Does the primerless process have high equipment requirements?

Yes. It requires good coating stability, high robot spraying precision, stable oven temperature control, and higher requirements for substrate flatness, otherwise defects are more easily exposed.

Difference between 3C1B and 3-Wet?

Both belong to the primerless compact process, with different emphasis in expression: 3C1B emphasizes three coats baked once, while 3-Wet emphasizes multiple layers sprayed wet-on-wet continuously.

Does the primerless process affect quality?

When substrate and electrophoretic quality are in place and the process is stable, quality is controllable; if sheet metal flatness is poor, omitting the primer will expose defects and actually make them more apparent.

Further Reading

• Functions and Application of Automotive Midcoat Primer
• Basic Process of Automotive Painting
• Low-temperature Curing Coatings and Energy Saving & Emission Reduction
• Automotive Coating VOC Emission Standards and Reduction Technologies

Kexin New Materials · Automotive Coating Technology Library | This article is technical Q&A content, for reference in selection and application

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