| Frequently Asked Questions |
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| How do hot dip galvanization and electro-galvanization differ? |
Galvanizing steel protects it from corrosion by coating the steel with zinc. The piece of metal being galvanized is called the substrate. There are two galvanizing methods:
- Hot-dip requires immersing steel in a vat of molten zinc. Hot-dip provides good resistance to corrosion, but tends to crack if the steel is bent. Hot-dipped steel is usually used where appearance and flexibility aren’t important.
- Electro-galvanizing produces a thinner, more attractive, flexible coating. In electro-galvanization, the steel is passed through an electrically charged plating solution, and the zinc is deposited more thinly and evenly.
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What are the standard descriptions for zinc coating weights? |
Electrolytic Zinc Coating - Minimum Requirements Per Side
ASTM: A591/A-591M-98
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Description |
Weight |
Thickness |
| |
SI units |
in/lb units |
g/m2 |
oz/ft2 |
micron |
mils |
| Flash |
03 G |
10 Z |
3 |
0.01 |
0.42 |
0.017 |
| Intermediate |
06 G |
20 Z |
6 |
0.02 |
0.84 |
0.034 |
| Full (Standard) |
12 G |
40 Z |
12 |
0.04 |
1.68 |
0.068 |
| Double |
24 G |
80 Z |
24 |
0.08 |
3.36 |
0.136 |
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| What are ID and OD? |
| A roll of steel is called a coil, and is described by its gauge (the thickness of the steel), width, weight, and internal (ID) and outside diameters (OD). These specifications are important in determining whether a coating supplier can work with a particular coil. |
| What's the difference between conversion, sealing, and passivation? |
| A conversion coating interacts chemically with zinc to add corrosion resistance. A sealer fills microscopic voids in zinc and zinc phosphate. Both conversion coatings and sealers may be painted. Passivation uses chromium to increase zinc's resistance to corrosion, and produces a surface that is not paintable. |
| What do single-source and toll work mean? |
| Single source means that we take care of buying the steel to be coated, unlike toll work, where we coat a customer's steel. |
| What do cutting, slitting, and oscillating mean? |
| After steel is coated, it is often slit or cut. Cutting, in the steel processing industry, means slicing the steel across its width. Slitting means slicing it into strips along its length. When steel is slit into narrow strips, it can be oscillated for the customer’s convenience in handling. Oscillating a steel strip winds it like fishing line on a reel or thread on a spool. As the steel is oscillated, the end of one strip is welded to the beginning of another, producing a compact coil containing a single strip of steel up to 25 miles long. This is also referred to as oscillator wound slitting. |
