Galvanizing as a method of protecting metal products
For corrosion protection of low-carbon and carbon steel, use:
- galvanizing;
- coated with polymer paint baked in an oven;
- polyvinyl chloride coating;
- combination: galvanizing + polymer coating,
- painting.
In addition to the supply of ready-made galvanized metal products: metal mesh, steel wire , gabions, Kazachka fidget, metal fences, we cover the metal products of our customers using hot and cold galvanizing.
Hot and cold galvanizing of metal products
There are two main methods of galvanizing metal products:
- hot dip galvanizing
- cold galvanizing
Both of these methods are used to protect the metal products we supply against corrosion. The amount of zinc on a metal product or metal structure after galvanizing is measured
- in g/m2 (specific density of zinc on the surface of the product);
- in microns (zinc thickness).
Hot galvanizing of metal products
In hot dip galvanizing, the metal product is dipped into a zinc melt.
Advantages of hot dip galvanizing
- In hot dip galvanizing, the zinc layer is large, so the corrosion protection is the highest;
- It is possible to increase the thickness of the zinc coating by double or triple dipping.
Disadvantages of hot dip galvanizing
- The hot-dip galvanized surface is not perfectly smooth. There may be influxes of zinc, thickening.
- High price
Cold galvanizing of metal products
There are two main methods of cold galvanizing:
- galvanic method (electro galvanizing);
- Zinganization method (coating with zinc-containing paint).
The zinganization method is used for galvanizing finished metal structures and it is very expensive, so we do not use this method to protect wire and wire products.
With the galvanic method, the product is immersed in a solution (not melt) of zinc salts and with the help of an electric current, zinc is separated from the salts and deposited on a metal surface: wire, mesh, etc. Therefore, often, cold-galvanized products are called electro-galvanized.
Advantages of electro galvanizing
- During galvanizing, the surface of a galvanized product is as close as possible to the surface of a non-galvanized product. Wire, mesh, metal fences during electro-galvanizing are as smooth as possible.
- Low price.
Disadvantages of electro galvanizing:
- A very thin layer of zinc 10-30 g/m2 leads to the fact that within a week to 7 years (depending on the equipment settings) the metal product begins to rust
Features of galvanizing welded meshes
In Ukraine, there is only equipment that allows you to weld a grid of galvanized wire .
In the price lists, they are indicated by indicating the density of zinc in the column "coating" from 30 to 50 g/m2 (for hot-dip galvanized wire) and 10 g/m2 (for electrolytically galvanized wire).
Therefore, welded mesh with increased corrosion protection (in the price list it is indicated 130 g/m2) is imported.
The grids are welded from galvanized wire, so they will start to rust 2 times faster than they will rust, for example, a chain-link mesh woven from the same galvanized wire.
This applies to any welded mesh made from galvanized wire, regardless of who produced it.
And that's why.
The grid is welded by resistance welding. In order for the galvanized wire to weld together, it must be heated with electrodes to the melting temperature of steel (1300 ºС) .
Zinc melts already at a temperature of 420 ºС, and evaporates at 906.2 ºС .
If you look at a welded mesh made of galvanized wire, you will see dark spots in the places of welding (photo on the right), with some technologies there may not be spots.
When asked about the absence of zinc, manufacturers will reassure you (and we were reassured) and say that if you rub your finger over the weld, the soot will be wiped off and you can see the zinc coating.
The way it is. We just went further. We decided to compare the corrosion resistance of galvanized meshes of Chinese and Ukrainian production, and the resistance of hot-dip galvanized and electrolytically galvanized meshes.
As expected, hot-dip galvanized grids turned out to be much more protected from electrolytically galvanized ones. Because there is much more zinc on welded meshes from hot-dip galvanized wire. We have made sure that the country of manufacture does not affect the corrosion resistance. The main thing is the amount of zinc.
But we also saw that all welded galvanized wire meshes begin to rust from the welding points and this happens much earlier than the galvanized wire itself begins to rust. (see video below)
CONCLUSION: When buying a welded wire mesh made of hot-dip galvanized galvanized wire, you must be prepared for the fact that it will begin to rust many times faster than the chain-link meshes from the same wire begin to rust.
This is not a marriage, this is a property of this type of grid.
Features of galvanizing mesh Chain-link
The grid the Chain-link in Ukraine is not subject to obligatory certification.
Therefore, the chain-link mesh can, according to Ukrainian laws, be produced with impunity from galvanized wire with a minimum specific density of zinc of 10-30 g/m2.
Such a wire can begin to rust after a year of operation.
It is impossible to make claims against the supplier, because it performs its functions - it encloses the territory.
We supply chain-link mesh according to GOST 5336-80, or from galvanized wire according to GOST 3282-74 . This means that zinc there is at least 50-70 g / m2, and such a mesh will serve for 15-25 years , and the first traces of rust will begin to appear during operation under normal conditions in 10 years.