Loctite thread sealants loctite 135490 loctite 566 has been designed for locking and sealing metal pipes and fittings it cures when confined in the absence of air between close fitting metal surfaces and prevents loosening and leakage due to shock and vibration loctite 566 can be used to seal against water oil and most common organic materials loctite 135490 566 thread sealant 50ml