Product Description

LOCTITE® 573™ is a medium-viscosity, thixotropic anaerobic flange sealant that cures between close-fitting rigid metal faces to seal the joint as a form-in-place gasket. The thixotropic nature keeps the green paste from migrating after it's applied, which gives more control over placement than a free-flowing liquid — a practical difference from LOCTITE® 515™, which runs at a much higher, non-thixotropic viscosity and suits wider or less controlled flange gaps. 573™ is typically used on rigid flanged connections like gearbox and engine casings, where a consistent, controlled bead matters more than raw gap-filling capacity.

How It's Used

Bond surfaces should be clean and free from grease. 573™ is designed for close-fitting flanged parts with gaps up to 0.25 mm, applied manually as a continuous bead, a rolled film, or by screen printing. For gaps greater than 0.125 mm, a rolled film applied with a pen roller to both flange surfaces is recommended. Low pressure testing (under 0.5 MPa) can confirm a complete seal immediately after assembly and before full cure. Flanges should be tightened as soon as possible after assembly to avoid shimming.

LOCTITE® 573™ is not recommended for pure oxygen or oxygen-rich systems, or as a sealant against chlorine or other strong oxidizers, and is not normally recommended for use on plastics — particularly thermoplastics where stress cracking could occur.

Storage

Store in the original, unopened container in a dry location. Optimal storage is 8°C to 21°C — storage below 8°C or above 28°C can affect product properties. Material removed from the container should not be returned to it once it may have been contaminated during use.

Safety

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This page summarizes performance data only. Consult the Safety Data Sheet (SDS) for full handling, storage, and safety information before use.

LOCTITE® is a trademark of Henkel Corporation in the U.S. and elsewhere.