During metal fabrication, it is advisable that welders avoid narrow gaps as much as possible because they will trap moisture and lead to rusting. As a newbie welder, you might think that galvanisation will prevent rusting in the space between overlapping metals. While this is true, it is essential to understand that zinc won't penetrate any gap that is less than 2.5mm because the metal is too viscous for spaces of that size. Furthermore, any cleaning solution used on the metal product will turn to steam and wash away the flux when dipped in a galvanisation bath.
Consequently, galvanisation baths creates bare areas that are prone to rust. In welding, you can't avoid metal overlaps during fabrication. Therefore, how do you protect the overlapped sections from rusting? Read on to find out.
Use a Sealant
If you are going to work with overlapping metal joints, it is vital to assume there is always going to be a gap between the overlapping metal substrates. One way to protect the surfaces of the overlapping metal pieces is to use a sealant. A sealant creates a barrier for infiltration or exfiltration of moisture and air; therefore, you are guaranteed that the hidden surfaces will stay watertight and airtight for a long time. Since sealants are made from polymers that allow for flexibility, you can use them in areas with a high likelihood of expansion and contraction such as metal substrates.
Use a Weld-Through Primer
As mentioned earlier, when two pieces of metal overlap their opposing surfaces become inaccessible to either powder coating or any surface finish. To get around the challenge, spray a zinc primer on the surfaces that are going to overlap before welding. Follow this by welding over the primer. Once done, spray some more of the zinc primer over the welded surface because welding burns off the protective paint thereby leaving the surface partially protected. By spraying more primer, you ensure the joint is rustproof.
As the name suggests, a seal weld will seal off overlapping metal surfaces. You merely weld along the edge of the overlap to achieve a seal weld. Therefore, seal welds preclude air and moisture from getting inside the cavity formed by two overlapping metal surfaces. While seal welds are a highly effective rust-prevention method, it is worth noting that they are not structural welds. Therefore, using more than enough weld beads will cause distortions of the final product. Additionally, you need to be careful where you place the overlap. For instance, incorrect positioning will lead users to believe the seal welds are structural; consequently, it will lead to overloading of the product which will compromise structural strength.
If you still have questions about the process, don't hesitate to contact welding services such as Burnback Welding Equip Services. They can ensure you know about various techniques or products that could benefit your welding process.