Body solder has long been the choice of custom and restoration shops for filling seams, leveling uneven body work, and blending-in custom features. Even the best polyester body fillers available today cannot match the superior adhesion, strength and overall durability that body solder provides. Both our leaded and lead-free body solders can be applied with an easily available propane torch.
Body solder melts at a relatively low temperature and is pushed or spread into position with a hard wood paddle to form the basic contour. Further shaping is usually done with a coarse file. Often a skim coat of polyester body filler like our Eastwood Contour Polyester Primer Direct to Metal Surfacer, and others, is applied over the solder for final shaping.
Traditional lead-based body solders have been the choice of restorers and customizers for over 80 years. All the lead-based body solder kits that Eastwood previously sold have used bars consisting of 30% tin and 70% lead. This mix produces a solder that is easily applied to vertical and horizontal surfaces, with a low spreadable working range (361° to 489° F). Tensile strength is 6140 psi. Tensile strength is sometimes referred to as Ultimate Tensile Strength and refers to the amount of force required to pull a substance apart. (In this case, a soldered joint that covers exactly one square inch would require 6140 lbs. of force to pull it apart). Body solders containing lead MUST be leveled by filing — sanding is never an option, because sanding lead-based body solder would put toxic lead dust in the air, and grit from the sandpaper may embed in the solder and cause corrosion. The low melting temperature makes the 30/70 lead-based solder slightly easier to use than our lead-free solder.
Lead-free body solder is a recent development that is safer and stronger than lead-based body solders. Our lead-free solder works well on horizontal and vertical surfaces. This solder’s spreadable (or “plastic”) range is 428° to 932°F (220° to 505°C), though the best working range is 535° to 660°F (280° to 350°C). Tensile strength is greater than 9000 psi. The increased strength makes the lead-free solder more appropriate for building-up door and other panel edges, and style lines. Leveling can be done by filing and sanding since no lead particles will be dispersed. (Be sure to wear a dust mask as you should for any metal-grinding operation.) This Eastwood formulation is one of the few solders that can actually be powder-coated and cured at 400°F (with accurate temperature control) without deforming. The fact that the lead-free solder can withstand powder-coating temperatures is a big benefit because it provides an alternative to Lab Metal for filling irregularities in iron and steel parts that will be powder-coated. Keep in mind that most of Eastwood’s powders are cured at 400°F — this is 28 degrees less than where this solder starts to soften. The solder is weak at 400°F but will not deform.
Both lead-based and lead-free body solders are applied similarly. Both need to be applied to clean bare steel. Both require tinning. Our tinning supplies serve the dual function of chemically cleaning the surface while depositing a thin coating of (mostly tin) metal, which provides an ideal bond to the subsequently applied solder. After wiping away the surplus tinning material, the surface is re-heated and solder applied. Once sufficient solder to level the surface has been applied, the area is re-heated and the paddle is used to level the repair. In the case of the lead-based solder, the paddle is used like a knife spreading butter. In the case of the lead-free solder, the paddle is used to push the solder into the surface. The “spreading” technique is not recommended in the case of the lead-free because impurities may become trapped..
Both body solders are applied in basically the same manner. If you can work in lead, you can work with lead free. The lead-free body solder has the advantage of being stronger and safer, and can be sanded and filed. Because of its slightly higher melting point, lead free solder is also suitable for powder coating.