Centennial, Colo. — The American Galvanizers Association (AGA) developed and released the Touch-Up and Repair of Hot-Dip Galvanized Steel online video series. These six short videos detail the specifications and methods used to touch-up and repair hot-dip galvanized steel. The videos provide highly beneficial visual aids to those needing assistance with touch-up and repair, whether in the plant or the field. Topics include proper materials to use while performing the process, as well as specifications to follow, and proper application of the repair materials.
Touch-up and repair is important in maintaining the hot-dip galvanized coating’s uniform barrier and cathodic protection, which ensures maintenance-free longevity. The first video in the series introduces the process of touch-up and repair of hot-dip galvanized coatings, and the reasons why items may need to be repaired. ASTM A780, Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings details three acceptable touch-up materials, zinc-based solders, zinc spray metallizing, and zinc-rich paints, which are covered in detail in later videos.
Touch-up and repair of galvanized steel is simple, whether in the galvanizing plant or in the field. The repair methods are the same, but in plant repairs have strict size restrictions found in the ASTM specifications. Field repairs should be kept to a minimum where possible, but there are no specific size limitations on repair areas. Two separate videos detail both in plant and in field touch-up and repair requirements.
The last three videos detail the three acceptable touch-up and repair materials: metallizing, zinc-rich paint, and soldering. Each video covers how to properly prepare the area to be touched-up as well as how to apply the selected touch-up material. Metallizing deposits molten zinc droplets onto the surface of a galvanized coating via a flame or electric arc and closely matches the appearance of the galvanized coating. Zinc-rich paints are the most commonly used repair materials, and can be either sprayed or painted onto the uncoated area. The last video covers zinc based solders. These zinc-based alloys blend well with the existing coating material and are applied by heating the surface and melting the alloy onto the heated metal.
For all repair methods, proper surface preparation should be performed before applying any touch-up material. Additionally, all touch-up methods are required to meet coating thickness requirements found in ASTM A123, A153, and A 767, and are dependent on the material used. The videos in this series are meant to be used as visual guides; however, it is advised to follow all applicable specifications while performing any touch-up and repair to hot-dip galvanized steel items.