What steel can be galvanized?
The following grades of steel can be galvanized: non-alloy carbon steel (e.g. PN-EN 10025-2), steel for concrete reinforcement (e.g. PN-EN 10080), low alloy steel of enhanced strength (e.g. PN-EN 10025-6), low alloy steel (e.g. PN-EN 10083-1), hot or cold rolled steel (e.g. PN-EN 10210-1, PN-EN 10219-1), which can be characterized with silicon content < 0.03% Si (with total silicon and phosphorus content not exceeding 0.04%) or when the silicon content is within: 0.14% to 0.25% Si. Quality of the obtained zinc coatings (gloss, smoothness, thickness, adherence, etc.) is different and depends on chemical composition; especially on content of carbon (C), phosphorous (P) and silicon (Si).
Content of carbon and silicon in steel should not exceed 0.5% in total. In case of silicon containing steel, sometimes it happens that the iron – zinc reaction is very intense and share of the iron-zinc alloy in the coating will be higher than normal. In extreme case, zinc coating can be completely composed of iron – zinc alloy. The phenomenon (so called Sandelin effect) can be observed with content of silicon 0.03% to 0.14% and above 0.25%. In these cases, zinc coating is usually mat and grey, rough, uneven, brittle – fragile to deformation and mechanical defects. Properties of zinc coating related to chemical composition of steel are specified by PN-EN ISO 14713-2. Appearance of the hot galvanized zinc coating on different steel is presented in the below table.
| Steel groups | Silicon content [%] | Appearance of hot galvanized zinc coating | |
|---|---|---|---|
| Low-silicon | up to 0,03 |  |
silver, glossy |
| Sandelin | from 0,03 to 0,14 |  |
grey, mat, rough, brittle |
| Sebisty | from 0,14 to 0,25 |  |
silver and glossy to mat and grey |
| High alloy | above 0,25 |  |
mat, grey, brittle |