Reactive steel is the term we use for steel that contains an unusually high level of silicon.
Very high or low silicon content in steel will increases the zinc coating thickness during the galvanizing process.
Silicon is usually added to steel as a deoxidant during its production and is an important part of that process. However, in some infrequent instances, when steel with high proportions of silicon is hot dip galvanized, the zinc-iron alloy layers that are normally one of the benefits of galvanizing continue to grow creating a very thick and sometimes unsightly darker finish. This darker finish conforms to the British Standards for hot dip galvanizing (BS EN ISO 1461 ) but is not visually appealing to some customers looking for a shinier finish. In some extreme cases the coating formed is so thick that it can be susceptible to handling damage. To a lesser degree the level of phosphorus in steel has a similar influence on the coating formation.
We recommend that the silicon content of steel that is to be hot dip galvanized should be between 0.15 and 0.25% and phosphorus be no more than 0.02% and you will find that most steel suppliers supply this as standard but if you have doubts it is best to contact your steel supplier for details.