PCB Accessories

518

LOCTITE 518 - Anaerobic Flange Sealant for Aluminum | Henkel

Henkel LOCTITE 518 is a single-component, medium-strength, anaerobic form-in-place flange sealant supplied in a 300 mL package, designed to cure between close-fitting metal surfaces and seal rigid flanged joints immediately after assembly. An anaerobic flange sealant is a type of adhesive sealant within the broader industrial gasketing and fluid-sealing hierarchy. Unlike pre-cut gaskets, a form-in-place sealant is dispensed as a liquid onto one flange face and cures in the absence of air once confined between close-fitting metal mating surfaces, conforming exactly to the joint geometry and eliminating gasket inventory and compression-set problems. Key features of LOCTITE 518 include its primerless curing capability, meaning no activator is required on most substrates; its semi-flexible cured film, which tolerates minor flange movement and micro-motions without losing the seal; and its thixotropic non-slump consistency, which reduces migration of the liquid product after application to the substrate. It also cures robustly even in the presence of minor surface contaminants, improving reliability in real production environments. Technically, LOCTITE 518 is formulated as a general-purpose anaerobic gasketing material for rigid iron, aluminum, and steel flanged mating surfaces, and is specifically highlighted by Henkel as ideal for aluminum substrates. It provides immediate resistance to low pressures after flange assembly, allowing downstream pressure testing or operation without extended cure waits. Its medium cured strength permits disassembly with standard hand tools, unlike high-strength retaining compounds that require heat. Typical applications include pump housings, gearbox and transmission covers, valve bonnets, compressor flanges, and engine timing or bearing-cap joints where machined metal flanges replace cut paper gaskets. Aluminum gearbox covers are a particularly common use case given the product's substrate affinity. Design consideration: keep the flange gap within the recommended range (typically below 0.25 mm for anaerobic cure on machined faces) and apply a continuous bead across the flange width; heavy contamination or oversized gaps slow the anaerobic cure. This page synthesizes distributor pricing, cross-referenced alternatives, and practical design notes not found in the manufacturer datasheet.