When two kinds of materials are glued together, the surface of each other is because of the glue to their mutual attraction, but the glue is not easy to fix, sticky not sticky with each other in the two materials are separated, because the adhesive is not easy to be fixed between the two materials, so bright surface and rough surface, not as good as the etching surface. Bonding is a surface phenomenon, when the glue is wet state, it can wipe off the surface of the material from the test
Welding is a metal chemical bond is formed between the solder and metal, solder molecules penetrate into the substrate surface metal of molecular structure, and the formation of a strong, completely metal structure. When the solder melting, it is impossible to completely from the metal surface to erase it, because it has become a part of the base metal.
Note: when soldering welding surface polished clean, tin. Site will then be welded together, with gas welding gun (fire to small) or electric iron heating so that the welding surface of the tin melting together. The increase in gap defect or thickness under the cover of dislocation, shell deformation is small but the appearance will be damaged, especially paint machine. Carefully use.