Sikaflex®-529 AT | Sprayable Seam Sealing and Stone Chip Protection Sealant for Vehicle Bodies

In the modern automotive industry, sealing products are expected to provide not only flexibility but also durability, paint compatibility, and ease of application. Sikaflex®-529 AT is an isocyanate-free, silane-terminated polymer (STP) based elastic sealant developed to meet these requirements.

Designed for professional use in vehicle body assembly and repair applications, it helps recreate original factory seam structures, provides stone chip protection, and improves acoustic damping performance.

Product Description

Sikaflex®-529 AT is a one-component, moisture-curing sealant based on STP technology. It can be applied either as a spray or bead.

It provides strong adhesion to metal surfaces, painted plastics, and automotive body components. The product contains no solvents, silicone, PVC, or isocyanates. Thanks to its low odor formulation, high flexibility, and paintable structure, it is suitable for both OEM (Original Equipment Manufacturer) production and aftermarket repair applications.

Application Areas

Sikaflex®-529 AT is used in vehicle body and automotive repair applications, including:

• Seam sealing on vehicle bodies (overlap joints and welded areas)
• Stone chip protection (underbody areas, wheel arches, side panels)
• Body component connection points and assembly joints
• Spray insulation applications in production and repair lines
• Elastic coating applications on metal and painted surfaces

The product stands out with its ability to reproduce the original factory surface texture and appearance.

Technical Properties (Summary)

• Chemical basis: Silane-Terminated Polymer (STP)
• Curing mechanism: Moisture curing
• Colors: Black, Beige
• Density (uncured): ~1.3 kg/L
• Skin formation time (23 °C, 50% RH): ~20 minutes
• Volume shrinkage: 3%
• Shore A hardness: 30
• Tensile strength: 1 MPa
• Elongation at break: 200%
• Tear resistance: 2 N/mm
• Service temperature: –40 °C to +80 °C
• Oven resistance: 120 °C (4 hours) / 140 °C (1 hour)
• Application temperature: +5 °C to +40 °C
• Optimum application temperature: +15 °C to +25 °C
• Packaging: 290 ml cartridge / 300 ml sausage
• Shelf life: 15 months for cartridges, 12 months for sausages (below 25 °C)

Main Advantages

Sikaflex®-529 AT provides significant benefits in automotive production and repair applications:

• Easy recreation of original factory seam textures
• Flexible application as spray or bead
• Low odor and free from isocyanates and solvents
• Excellent sag resistance for vertical applications
• Compatible with water-based paint systems
• Strong adhesion to metal and painted surfaces
• Vibration and acoustic damping properties
• Silicone and PVC-free formulation

Application Method

Surface Preparation

The surface must be clean, dry, and free from dust, oil, grease, and contaminants.

For long-term performance, appropriate surface preparation procedures should be followed, and an activator should be used where necessary.

Application

• Application temperature should be between +5 °C and +40 °C.
• Suitable spray equipment should be used for cartridge application, while appropriate dispensing equipment is required for sausage packaging.
• The product can be applied as a spray texture or as a bead using manual or pneumatic guns.
• The optimum application temperature is between +15 °C and +25 °C.

Tooling and Surface Texturing

The surface texture can be created with a spatula or brush within the skin formation time (approximately 20 minutes).

Paintability

• Can be painted during skin formation or after full curing.
• If oven curing is required, the sealant must be fully cured beforehand.
• Due to differences in elasticity between paint systems and sealants, compatibility testing is recommended.

Cleaning

• Uncured material can be removed using a suitable cleaner.
• Once cured, it can only be removed mechanically.
• Solvents should not be used for skin cleaning.

Limitations

• For professional use only.
• Do not apply below +5 °C.
• Testing is required before application on plastic surfaces with stress cracking risks.
• Oven heating should not be performed before complete curing.

Conclusion

Sikaflex®-529 AT is a sprayable STP-based sealant developed for vehicle body seam sealing, stone chip protection, and insulation applications.

With its environmentally friendly formulation, paintable structure, and elastic performance, it provides a powerful and reliable solution for professionals who need to recreate original automotive body textures in both manufacturing lines and repair workshops.

Frequently Asked Questions (FAQ)

What is Sikaflex®-529 AT?

It is an STP-based, isocyanate-free, sprayable elastic sealing compound designed for automotive applications.

Where is Sikaflex®-529 AT used?

It is used for vehicle body seam sealing, stone chip protection, and automotive repair applications.

How is it applied?

It can be applied by spray equipment or as a bead using manual or pneumatic dispensing guns.

Can it be painted?

Yes. It is compatible with water-based paint systems.

What color options are available?

It is available in black and beige colors.

At what temperatures can it be applied?

It can be applied between +5 °C and +40 °C and provides short-term resistance to elevated temperatures.