HSS galvanizing is gaining in popularity. Most steels can be satisfactorily hot-dip galvanized, but reactive elements in the steel like silicon and phosphorus can affect the process. The right composition will give a more consistent quality of its appearance, thickness and smoothness. The Sandelin Curve compares zinc coating thickness to the mass percentage of silicon in the steel. The old misconception that silicon content levels had to be below .03% for galvanization no longer applies. The recommended silicon composition is either less than 0.03% or between 0.15% and 0.25%. Any steels not within these ranges are considered reactive steels and can be expected to form thicker than average zinc coatings.
During steel production, silicon or aluminum is added to remove oxygen. The resulting steels are known as “killed steels,” while steels produced without these additions and are called “rimming steels”. Ideally, assemblies should consist of elements of similar chemistry and surface condition. Whenever different analyses of steel or different surfaces of steel are united in an assembly, the galvanized finish is not generally uniform in appearance. The silicon content in steel must always be analyzed and considered since it affects the hot dip galvanizing reaction. Aluminum-killed steels suitable for galvanizing have a low silicon content, below 0.03%. Silicon killed steels with a silicon content above 0.14% can work well in galvanizing, but give a thicker coating than aluminium killed steels. Semi-killed steels with a silicon and phosphorus content ranging from 0.03% to 0.14% are called sandelin steels and should be avoided.
Nucor Tubular Products does not galvanize in-house, but can arrange to have your items galvanized prior to shipment.