Duralac is a chromate containing jointing compound designed to inhibit electrolytic decomposition between dissimilar metals – often called galvanic corrosion. It is a single pack, air setting product. Used correctly, Duralac prevents anodic decomposition.
Duralac is a free flowing paste based on a synthetic elastic resin and barium chromate. Duralac conforms to specification DTD 369B, which superseded DTD 369A
Duralac has low solubility in water and will not erode with time, even when subjected to high pressure from considerable water flow. Duralac enjoys excellent adhesion properties to most substrates and because of its tough flexible composition, has very low water absorption. Duralac has a two year shelf life from the date of dispatch when stored below 20°C. Once a container is opened, the remaining Duralac will form a skin.
Duralac is indispensable for the sealing of joints between dissimilar metals of all types, including magnesium and its alloys. Consideration should also be given to galvanic corrosion of the same metal where the electrolyte varies in concentration forming a concentration cell. Duralac has excellent protection properties for metals in contact with wood, synthetic resin composition, leather, rubber, fabrics etc. When components of a structure are of different materials, it is essential the ‘points or faces’ of contact be treated with Duralac to inhibit corrosion in the presence of an electrolyte where considerable differences in potential arise. Components of the same metal in contact with one another under different stresses will also benefit from the use of Duralac to inhibit corrosion.
For example Duralac may be used:
•Between aluminium alloy plates, extrusions and bolts or rivets used in building applications.
•In general engineering applications where dissimilar contact cannot be avoided.
•In vehicle building where aluminium alloy contacts steel.
•For marine application where corrosion is accelerated by brine concentration.
•In close proximity to the sea where a salt laden atmosphere will meet with structures and set up electrolytic cells.
•In aerospace where rivets/bolts are secured into aluminium plates.
Duralac is supplied ready for use and must not be thinned. It is best applied by brush. When Duralac is applied to metal or other surfaces the volatile solvent evaporates and the compound sets to the touch, but remains tacky for a considerable period. It is important that the joint should be closed while Duralac is still tacky to ensure that it will flow sufficiently under pressure to close the gaps in the joint. It will harden somewhat if a thin film is left exposed to the atmosphere for a long period and this will prevent the making of a close joint.