How to Repair Galvanized Coatings

Repair Using Zinc Based Alloys

1. Be sure that you have the Galvanite Instructions and be sure to read them.

2. Pre-clean the parent metal. Use these items: emery cloth, a wire brush, sandblasting, etc. Cleaning galvanized steel surfaces is often done with a stainless steel wire brush. To ensure a smooth surface result, surface preparation should extend into the surrounding undamaged galvanized coating. Breaking the oxide layer by agitation is an important key to successful galvanizing repair. If the area to be repaired includes welds, all weld flux residue and weld spatter shall be removed by wire brush, chipping, grinding or power scaling.

3. Use a soft flame, heat gun or soldering iron to heat the parent metal repair area to at least 600°F/315°C. Do not heat the surface over 750°F/400°C or allow the surrounding galvanized coating to burn. If you use a direct flame, keep it moving. A direct flame held on the repair area is likely to overheat the solder. Wire brush the surface during heating. Pre-flux using flux if there is an adhesion problem. NOTE: Many applications do not require flux.

4. Hold the torch tip 4 to 6 inches (10.2 to 15.2 cm) away from the parent metal. If it is necessary to apply the flame directly to the rod to get it started, pull the torch tip back even farther from the work surface and keep it moving.

5. Drag the rod over the area to be soldered, until it begins to flow. Once the rod flows, stop applying the heat. Deposit the desired thickness of galvanizing repair rod. A stainless steel brush works well to spread the solder and ensure it is adhering. If additional layers are needed, continue to drag the rod over the area.

   1. Bring back the heat only to keep the surface, not the rod, hot enough to push the solder around to where you want it.

6. Blend the repair into the undamaged galvanized coating. The most common oversight in repairing galvanized is failing to feather the galvanizing repair material layer into the undamaged galvanized coating. If they don't join in sufficient thickness to form a seamless barrier (skin), corrosion will occur right where they meet.

7. Observe the solder deposit. The solder should bond smoothly. Do not overheat, the solder rod will melt if overheated, but will not bond properly. Spread the solder deposit evenly over the repair area. A stainless steel brush works well for this step.

8. If you stopped soldering and want to apply more solder or flow out the deposit more, let the area cool below the solid temperature and reheat. The existing coating will help the bonding process, whether adding more solder or just flowing out the previous deposit.

   1. If substantial time has elapsed since the original repair layer was applied, pre-clean the repair area again to remove any oxide coating that will impair bonding. Again, a stainless steel brush works well for this step.

9. Smooth the repair area and remove any excess solder with a wire brush.

10. Repeat these steps to build up additional layers of protection.

11. Gather the materials below:

    1. Common Zinc based alloys
       1. Zinc-Cadmium – Liquid temperature - 509°F-600°F (265°C-316°C)^[1]
       2. Tin-Zinc-Lead – Liquid temperature - 350°F-550°F (177°C-288°C)^[2]
       3. Tin-Zinc-Copper – Liquid temperature - 390°F-570°F (200°C-300°C)^[3]
    2. Propane or MAP Gas torch is recommended
    3. Stainless steel or wire brush