All types of structural steels, low-alloy steels, and forged, cast, etc. iron and steel products can be galvanized. However, there are some requirements for them to be galvanized. The alloying elements in the chemical composition of the iron and steel materials to be galvanized affect the physical and chemical properties of the coating. These effects can be listed as follows:
- CARBON: It has no significant effect on coating appearance or thickness. However, in steels with high carbon content, the material can absorb hydrogen when placed in an acid bath for surface cleaning, which may lead to hydrogen embrittlement.
- MANGANESE: Steels with high manganese content produce a thick coating with low impact resistance. This is unfavorable both aesthetically and in terms of coating quality.
- SILICON: Silicon in the steel has an adverse effect on the thickness and appearance of the zinc coating. Outside certain value ranges, an extremely thick and matte coating is obtained. A thick coating weakens coating adhesion, and flaking may occur.
- PHOSPHORUS: Steels with high phosphorus content produce a thick coating that is prone to cracking.
Note: Brass- and bronze-welded, soldered, and aluminum-riveted materials are not suitable for galvanizing. When these materials are immersed in the molten zinc bath at 450°C, uncoated areas, melting, and similar defects occur on those surfaces.
The high silicon content of steel materials plays a major role in determining the thickness and color of the galvanized coating. The material in the photos below was dipped into the galvanizing kettle as a single piece. Because of the difference in chemical composition, namely its higher silicon content, the elbow section welded onto the pipe reached a higher coating thickness than the other parts, and its coating has a matte appearance. As the graphs show, we have tried to illustrate the coating thicknesses formed when materials with different silicon ratios are galvanized under the same conditions, and how strongly silicon determines the color of the coating.
