The most common reason for impregnation of castings is to enable parts to retain fluids under pressure. Examples are automotive steering gear housings which retain hydraulic oil up to thousands of KPa, fuel system pumps, regulators and filters with all kinds of fuel under pressure, cylinder heads and coolant pumps retaining various coolants, hydraulic pump and motor parts, refrigerant compressor parts, gear cases, air brake components, hydraulic door closers and gas meters. Properly impregnated, these parts are permanently sealed and can hold pressures up to the burst strength of the casting.
Castings are also impregnated to seal porosity in preparation for metal finishing operations such as painting or plating. If the pores are not sealed, foreign fluids may be absorbed that remain in the pores through the finishing operations. These trapped fluids may emerge later, attacking the finished coating from within and causing pits, blisters or other blemishes in the finish. The “Blowouts” that occur in paint curing ovens are often caused by gases or liquids emerging from pores. Some effects of porosity may not appear in the surface finish until well after processing has been completed. Impregnation of castings before the finishing operations will seal the pores so that foreign fluids cannot be absorbed.
In some instances, it may be desirable to seal the pores in a casting so that corrosive fluids cannot enter. This is done to prevent corrosion that may originate within the porosity. Even though the surface of the part has been treated to prevent corrosion, stains may appear on the surface of the part from internal corrosion. Impregnating such a part will help to seal out corrosion that might otherwise occur inside the pores.
The unique self-curing capability of Loctite’s Resinol RTC has made this the most reliable material for sealing porosity in metallic and non-metallic parts. This system uses an anaerobic resin that cures to an impermeable thermoset plastic.
The ability to cure without heating the parts, combined with use of the ‘Activator’ rinse, gives the anaerobic sealant much greater capability in sealing a wide range of pore sizes, especially larger pores. Bleed-out of sealant will not occur with Resinol RTC, so fouling of a part does not occur and sealing performance is consistently high.
The cured material is impermeable to most substances including gasoline, antifreeze, engine oil, transmission fluids, cleaning solvents, caustic cleaners, acids, road salt and grit. The cured resin is stable between -54oC to +232oC, will improve the insulation of electrical and electronic components and meets Mil-l-17563C Class 1 & 3.
The certainty of self-curing by Resinol RTC assures that parts that have been impregnated will be properly sealed. The curing process is not dependent on operator control.
Resinol RTC incorporates 100% reactive washing agents that ensure excellent removal of excess resin in plain, detergent-free water.
Loctite is a registered Trade Mark of the Henkel Corporation, USA
Advanced product designs and new manufacturing techniques require modern methods for sealing micro-porosity in metal castings, powder-metal parts, electronic components, plastic composites, welds, and other porous substrates.
Vacuum impregnation as a means of reliably sealing porosity in a variety of substrates has now been available for a number of years.
The ability to permanently seal pores in a cost-effective manner has elevated this former ‘fix-it’ into a trusted manufacturing process and important design tool.
Previous resin impregnation materials discouraged manufacturers because they fouled parts with sticky residues, produced inconsistent sealing results, had poor long-term reliability, and created fears of environmental problems.
The Loctite Resinol RTC system has eliminated the majority of these problems.