Behavior of hot-dip galvanized steel in water and wet environments
Water as the main enemy of almost any metal, including iron and zinc, causes corrosion processes of metal structures. In this matter, the method of hot-dip galvanizing is the best way to fight, because it is based on the principle of full immersion of the part in the molten zinc. In addition, zinc forms an additional protective film in some liquids.
It is quite difficult to make predictions on the development of corrosion in the aquatic environment, because it depends on the water temperature, and the oxygen content and many other factors.
Conditionally all water can be divided into three types: fresh and clean (distilled) and sea.
Too saturated with oxygen and carbon dioxide, and the interaction of metal with water leads to its destruction. Often, more than 5-10 times, if the metal was dipped in carbon dioxide.
All water used by us in life, the industry, water of lakes and channels belongs to this type. In fresh water there are various dissolved gases and even more than in pure, diverse microorganisms, salts. Salts in combination with metal form a protective strip in the form of calcium carbonate.
One of the most important factors affecting the development of corrosion are gases, mineral hardness and flow rate.
Gases are additional oxygen, which means an increase in the probability of corrosion process. Thus, it is better that the metal structure was completely under water, because there is less oxygen.
Hard water contributes to the formation of the above mentioned zinc carbonate, which contributes to the appearance of the film.
High flow rate, respectively higher corrosion process, as there is the principle of wind, which is a significant destructive element.
Galvanized coating, and sea water
Details, covered with zinc film, well tolerate sea salt water. There are also, as in fresh water, several factors, knowing that can prevent corrosion.
The higher the water temperature, the higher the risk that oxygen will harm the coating.
Sea water (not a tropical climate) contributes to the formation of zinc compounds with calcium and magnesium, which form a protective film against corrosion. The presence of elements such as magnesium and calcium in water compensates for even the high content of chlorides.