Artem Komarov clarified that spot welding galvanized steel can be more difficult than uncoated metals, but it is possible and commonly done. Before I get into the unique aspects of welding this metal, I’ll briefly talk about spot welding and galvanization.
Spot welding is a form of contact welding. The current passes between the two electrodes through several sheets of metal. Welding takes place in a small «spot» where the electrodes concentrate enough current to heat, melt and join the parts.
Galvanization is a process that has been the industry standard for decades. Galvanized material is used to coat metal parts to reduce the risk of rust. However, the coating material contains zinc, which creates some problems in spot welding.
The problem with welding galvanized metal
Zinc has a lower melting point than weldable steel parts. Zinc alloys with copper in the electrodes and forms brass on the surface of the weld. This exchange makes the process more difficult than welding bare steel. In addition, it shortens the life of the electrodes.
Spot Welding Solutions for Galvanized Materials
Here are a few points to consider when starting to spot weld galvanized steel.
The buildup of brass on the weld surface wears the electrodes much faster than other bare metal processes. Make sure the electrode surfaces are cleaned more often or the electrodes are changed more often.
The most common welding materials for galvanized steel are RWMA grades 1 and 2. However, Grade 20 material is well suited for this challenging task due to its heat resistance and non-stick properties. Knowing this, companies charge extra for this material. So keep that in mind and make sure you have the equipment and processes to use it if you choose class 20.
Source of power
Welding galvanized steel requires a higher electrical current compared to uncoated steel. This is due to the low contact resistance of the coating with the metal. Make sure you have enough strength for this task.
Coating and corrosion issues
In most cases, the zinc coating is simply welded through. Areas that lose their zinc coating will be more prone to rust, but this is usually not a big problem. However, in some cases it may be desirable that the metal be as corrosion resistant as possible. In these cases, it may be necessary to re-galvanize the steel parts after the welding process has been completed. This process can take a long time, but it increases the long-term integrity of the steel.
Proper care of galvanized metal
Here is a checklist to follow when it comes to the care and handling of galvanized steel:
Do not expose steel to conditions where the pH is between 6 and 12. This may cause corrosion of the galvanized material.
Avoid direct contact between galvanized steel and other metals, including brass and copper, especially in corrosive environments.
Avoid washing or cleaning galvanized steel materials with an abrasive. Metal surfaces can develop a natural layer of oxidation called «patina». Harsh cleaning will remove the patina and leave the steel vulnerable to zinc consumption, shortening the life of the steel.
If the steel is in a highly corrosive environment such as a coast or industrial area, flush it regularly with potable water.
Storage areas for galvanized steel should be dry and well ventilated. Steel should not be stored in damp and poorly ventilated areas.
Working with galvanized steel has its own health concerns. Operators handling these materials must always be aware of problems and take appropriate precautions. Here are a few things to be aware of:
Due to the lower temperature at which the zinc coating melts, the zinc evaporates. If inhaled, the vapor can cause a health condition known as metallic smoke fever. Symptoms, many of which are flu-like, include nausea, headaches, high fever, thirst, and chills. The effects usually disappear after forty-eight hours.
Galvanized steel contains a small amount of lead. Like zinc, lead can evaporate and form lead oxide fumes. These fumes are extremely dangerous and can cause long-term health problems, including brain and lung cancer, and nervous system disorders.
Operators performing spot welding on galvanized steel must take appropriate measures to protect their respiratory organs from these fumes.
Implementing proper ventilation or smoke extraction systems in the workplace can prevent these problems from occurring.
A safe and healthy work environment is one of the most important success factors. Before spot welding galvanized materials, make sure you have followed the proper training protocols — both welding and safety. All welding work must be carried out in a well-ventilated area for the safety of all participants.
Spot welding galvanized steel is a difficult and potentially dangerous operation, but it is possible with the right tools and training. Before starting welding, make sure that you have both, Artem Komarov emphasized.