YOU MUST DEMAND YOUR STEEL SUPPLIER TO SELL STEEL WITH RIGHT CHEMICAL CONTENT WHAT IS SUITABLE FOR STEEL GALVANIZATION. DO NOT RISK WITH THE QUALITY!
It is possible to hot dip various of carbon and cast irons, but results may be very different. There will be chemical reaction between steel and zinc layer what improves connection with eachother, but this result is affected strongly with choice of steel. Every steel has is own chemical compositon. In recent past the usage of galvanizing were so rare in our region and steel producers and buyer didn’t had knowledge what chemical content in steel guarantees the best results for galvanization. Eastern metal factorys do not pay attention on the content of the silicon and phosphorus in steels. Unfortunately these two compounds affects most the quality of galvanization. Both Silicon and phosphorus is nessesary alloys without you can not galvanize ,but their content in steel is for quality results is exactly regulated.
Steel with low consists of Silicon (Si < 0,03%) is visually perfect after galvanisation process (shiny and bright) , but it is more difficult to achive the results what is needed for filling the requirements (EVS-EN ISO 1461).
Besides the low content of Silicon it is nessesary to notice the content of phosphorus in steel and witch way steel is rolled.
Cold rolled steel:
Si < 0,03% ja Si + 2,5 x P < 0,04%
The consist of Silicon is more important when steel is Hot rolled and less important is the content of phosphorus:
Si < 0,02% ja Si + 2,5 x P < 0,09%
If silicon and phosphorus content is more or less than mentioned scope then it fall into so called Sandelini phenomenon (look graphic, Si < 0,15%).
Galvanizing quailty will be very poor with this kind of steel. Zinc layer is very thick and fragile. Surface may peel off.
Steel with avarage content of silicon (Si = 0,15 – 0,22%) are very good for galvanization. Zinc layer is light gray and thickness is allowe by the standard EVS-EN ISO 1461.
Steels with higher content of silicon (Si = 0,23 – 0,30%) may be used to achive more thicker layer of zinc, but must be consider that the zinc layer is more fragile and visually not so good. Extra attention is needed when transporting and loading and unloading these details.
Steels with very high content of silicon Si > 0,30% no longer can use for galvanization. Zinc layer will be very thick ( over 200 µm) and fragile and uneven. Surface may peel of anytime.