7 key differences between cold galvanizing and hot-dip galvanizing
This article will go through 4 main sections:
- The difference in terms
- The difference in the galvanizing condition
- Technological difference
- Environmental problems
1. Hot-dip vs Cold galvanizing technology: The difference in the basic definition
Before going into the conceptual comparison of the two galvanizing methods, let’s look at the concept of galvanizing. The galvanized surface is a metal surface covered with a layer of zinc to resist corrosion. This method is usually applied to two metals, steel, and iron.
1.1. Cold Galvanizing
“Cold galvanizing” or “plating” is a solution of zinc salts by electrolysis to create a coating on the surface of the metal. This method does not require heating and uses a small amount of zinc, making it easy to peel off in a humid environment. This is a method of physical impact.
1.2. Hot-dip galvanizing
Hot-dip galvanizing is a chemical approach, an electrochemical reaction between the reactants and the metal surface. The hot-dip galvanizing method produces a coating whose adhesion is extreme, does not fall off easily, and its durability also lasts a very long time.
2. Hot-dip vs Cold galvanizing technology: The difference in the galvanizing condition
2.1. Hot-dip galvanizing
Hot-dip galvanizing is the process of dipping metal (usually iron and steel) into a bath of zinc-containing molten zinc at a temperature of 450 ºC. In this process, zinc with steel forms an alloy and an unbreakable coating. However, it requires a thoroughly cleaned steel surface; otherwise, it will cause prominent black spots on the galvanized coating.
For the desired zinc coating, the input material must meet the following four primary conditions:
- Steel quality must meet NEN-EN-ISO-1461 standard;
- Ventilation and drainage holes and hanging holes must be appropriately designed, installed, and located;
- The material shall be free of impurities that are difficult to remove by standard treatment methods;
- The material does not have a combination of galvanized steel and untreated steel.
2.2. Cold Galvanizing
Cold galvanizing should be done outdoors or in a well-ventilated area such as an open garage. To ensure proper drying, it is recommended to perform in an environment with temperatures between 50-90ºF (10-32ºC) and humidity below 65%. Do not apply to surfaces that exceed 200ºF (93ºC) when heated. We do not spray galvanized = in solid wind and dust conditions, and at the same time, it is necessary to shield the area around the construction site.
3. Hot-dip vs Cold galvanizing technology: The difference in the technological aspect
Hot-dip galvanizing is to degreasing the workpiece, pickling, dipping, and drying the liquid soaked in molten zinc for a particular time.
Cold galvanizing uses electrolytic devices to degrease, soak the component in a zinc salt solution, and connect the positive electrode. In place on the parts of the zinc plate attached to the positive electrolytic device, turning on the power, applying current from the cathode to the anode of the directional movement of the workpiece deposited in a zinc layer.
4. Hot-dip vs cold galvanizing technology: Environmental issues resulting from the galvanizing process
Hot-dip galvanizing causes fewer emissions than cold galvanizing. Pollutants released from hot galvanizing are mainly from waste pickling.
Pollutants caused by cold galvanizing include components of acid pickling waste, electroplating waste, and passivation liquid waste. This method releases more contaminants than hot-dip galvanizing.
With the content we have provided above, we hope you have grasped the fundamental differences between hot-dip galvanizing and cold galvanizing. Hot galvanizing is generally more durable, while the other one is cheaper. The choice depends on your needs and budget.