calcium alginate

1b.welding rods Coatings are applied to welding rods or electrodes to act as a flux and to control the conditions in the immediate vicinity of the weld, such as temperature or oxygen and hydrogen availability. The dry ingredients of the coating are mixed with sodium silicate (water glass) which gives some of the plasticity necessary for extrusion of the coating onto the rod and which also acts as the binder for the dried coating on the rod. However the wet silicate has no binding action and does not provide sufficient lubrication to allow effective and smooth extrusion. An additional lubricant is needed, and a binder which will hold the damp mass together before extrusion and maintain the shape of the coating on the rod during drying and baking. Alginates are used to meet these requirements. The quantities of alginates used The quantities of alginates used are very dependent on the type of welding rod being coated and the extrusion equipment being used. For soluble alginates it may be 0.4-1.2% or low-hydrogen welding rods and 0.15-0.25% for acid and organigc types. For the thixotropic alginates, manufacturers often find it more effective to use a mixture of calcium alginate and sodium alginate with a total alginate content of 0.4-0.6% for low hydrogen electrodes.