Two silicone sealants can carry the same name, the same cure time and the same price, and still fail in completely different ways. The difference is the cure chemistry: acid cure (acetoxy) silicone releases acetic acid as it cures, while neutral cure silicone does not. That single difference decides which substrates you can safely use it on, and whether the finished joint will still look good in a year.
- Acid cure silicone releases acetic acid vapour while curing, which attacks coated and anodised metals, mirrors and limestone.
- Neutral cure silicone has no acidic by-product, making it the default for building substrates and coated profiles.
- Acid cure typically skins over faster in good conditions, which is why it persists in some assembly work.
- Neutral cure is more tolerant of difficult substrates and less well-ventilated spaces.
- Cure type must be matched to the substrate, not to the sealant brand or the price.
What acid cure damages
- Coated and anodised aluminium — dulling and eventual corrosion at the joint
- Stainless steel and other metals — corrosion over time
- Mirrors — the reflective backing layer reacts with the acid, producing permanent black spotting at the edge
- Limestone, marble and other calcium-based stone — acid etching leaves the surface dull and whitish
Neutral cure: the practical default
Neutral cure silicone sealant is what most facade, window, door and general construction specifications call for, because the substrate mix on a building is mixed — glass, aluminium, stainless steel, coated profiles, stone, tile — and neutral chemistry is compatible with all of them. Our PR-666 neutral silicone sealant is a neutral grade for interior and exterior joints, and the curtain wall and facade application page shows where it is typically used.
PIROI PR-666 neutral silicone sealant — specifications
Test report 2025ME156, tested to GB/T 14683-2017. A neutral cure silicone sealant for interior and exterior joints, weatherproof, high strength, suitable for curtain wall and general sealing.
- All-weather performance for interior and exterior
- Neutral cure, non-corrosive to materials
- Excellent adhesion to common building materials
- High strength and weatherproof sealing
- Good compatibility with other neutral silicone sealants
- Transport as non-hazardous goods
- Shelf life 12 months; 300mL cartridge and 590mL sausage packaging
Typical applications
- Curtain wall weatherproof sealing
- General construction joints
- Metal and glass facade sealing
- Window and door perimeter sealing
Application notes
- Do not apply on damp surfaces
- Not for oily or exuding surfaces
- Not for unventilated areas
- For joint sealing — not for structural bonding
PIROI is a silicone sealant manufacturer in Zhongshan, China, with a neutral cure series and an acetoxy series covering facade, window and door, sanitary, industrial and fire-rated applications. We support OEM and private label packing, sample testing before bulk orders, and full-container export. Contact us for the PR-666 data sheet, MOQ and lead time, or the certifications and test reports we hold.
