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 Stale niskokrzemowe silver, glossy
Sandelin from 0,03 to 0,14 Stale Sandelinowskie grey, mat, rough, brittle
Sebisty from 0,14 to 0,25 Stale Sebiste silver and glossy to mat and grey
High alloy above 0,25 Stale Wysokokrzemowe mat, grey, brittle