Sika SikaBiresin® AP077 + BPO Cream Hardener - White - Quart

Sika SikaBiresin® AP077 + BPO Cream Hardener in white is a professional-grade gelcoat repair system designed for marine applications both above and below the waterline. This one-quart hardener works as the catalyst for polyester or vinyl ester resin, enabling fast-setting repairs on fiberglass hulls, stringers, and structural components. Engineered for boaters and marine repair professionals who need durable, long-lasting results without the complexity of two-part epoxy systems.

The AP077 formulation delivers high heat resistance rated to 400°F (209°C), critical for engine compartments, exhaust routing, and areas exposed to radiant heat. Low moisture absorption makes it suitable for waterline repairs where hydrolysis could compromise bond integrity—essential for offshore vessels and saltwater fishing platforms spending extended time at sea. The cream hardener applies easily, sands without gumming or clogging, and accepts virtually all topcoat finishes including polyurethane, epoxy, and standard marine paints. Minimal shrink and sink upon cure means repairs cure true without surface depressions that require re-sanding or additional filling.

This hardener bonds reliably to epoxy, vinyl ester, polyester, and multiple substrate types—making it versatile for patch repairs, structural reinforcement, and cosmetic restoration on both recreational fishing boats and working commercial vessels. The quick-set characteristic reduces downtime for anglers who need their boats back in the water or for professionals managing multiple repair jobs. Weekend boaters tackling hull damage, impact repairs, or delamination issues will appreciate the straightforward mixing and application process that doesn't require specialized equipment or extended curing schedules.