Hoseki Adhesion Promoter

Product Overview
Achieve unparalleled adhesion on your toughest automotive projects with Hoseki’s Adhesion Promoter. Formulated to work seamlessly under primers on both flexible and rigid plastics, it also excels as a reliable tie-coat between fresh or existing primers and color coats (single stage or basecoat). It is the go-to choice for dependable performance on a wide variety of challenging substrates.

Suitable Substrates
• Raw Plastics: Rigid (SMC, BMC), Flex (ABD, PPO), Soft (PUR)
• Primed Surfaces: Plastic parts (primed), 1K & 2K primers, Self-etching primer
• Metals: Bare steel, Bare aluminum
• Other: Body filler, OEM finish & old paint work (non-reversible), Fiberglass / SMC gel coat

Note: Due to the diverse nature of plastics, always test the substrate for acceptable adhesion. Test pre-primed panels with acetone or paint thinner; if the coating fails, strip the panel to bare plastic and follow standard operating procedures for raw plastic.

Surface Preparation & Application

1. Cleaning & Sanding
• Plastics: Clean thoroughly using a plastic cleaner or scuff & prep paste with a scuff pad to enhance repair material performance. Rinse with water and wipe dry with a clean cloth.
• Fresh/Aged Primer or Existing Finishes: Sand primer with 400-500 grit paper (hand block or DA). Clean thoroughly using a high-quality degreaser.

2. Application Guidelines
Mix Ratio: Ready to Use
• For Plastic Parts: Apply 1 medium coat. Allow a 20–30 minute flash time before topcoating or priming. Apply primer, color, or clearcoat directly to the adhesion promoter.
• For Fresh/Aged Primers or Existing Finishes: Apply 1 medium coat (use 2 medium coats with a 5–10 minute flash if applying over polyester primer). Allow 20–30 minutes to flash before topcoating.
• For Aluminum or Steel: Test a piece first to ensure adhesion across different metal grades. Apply 2 coats, allowing a 5–10 minute flash between coats. Dry for a minimum of 20–30 minutes (allowing more than 30 minutes greatly improves adhesion). Recoat window is up to 24 hours. Apply 2 coats of any Hoseki clearcoat (accelerator additives are strongly discouraged). Allow 24 hours to cure before testing adhesion via the cross-hatch/tape method.

Flash & Dry Times
• Flash between coats: 5 – 10 minutes
• To prime / topcoat: 20 – 30 minutes

Gun Setup & Air Pressure
• Siphon Feed: 1.2 – 1.6 mm | 35 – 45 psi
• Gravity Feed: 1.2 – 1.4 mm | 25 – 35 psi (@ regulator)
• Pressure Feed: 1.0 – 1.2 mm | 40 – 50 psi (Fluid: 8 – 10 psi)
• HVLP / LVLP: 1.2 – 1.5 mm | 10 psi (@ aircap)

Product Specifications
• Color: Amber
• Available Sizes: Gallon (HSK70031), Quart (HSK70034), 16 oz Aerosol (HSK100016)
• Shelf Life: 3 Years
• Mix Ratio: Ready to use
• Regulatory Category: Adhesion Promoter
• Density: 7.29 lbs/gal
• Wt % of Volatiles: 88.29%
• Wt % of Water: 0%
• VOC Actual: 4.78 lbs/gal (573 g/l)
• VOC Regulatory: 6.58 lbs/gal (788 g/l)
• Wt % Exempt Compound: 22.76%
• Vol % Exempt Compound: 27.36%