In short
Black sheet is hot-rolled with its oxide scale; HRP is the same sheet pickled and oiled; DKP (cold-rolled) is pickled sheet rolled again at room temperature for tighter thickness and a smooth surface; galvanized sheet is coated with zinc for corrosion protection. Only galvanized sheet carries its own protection against rust.
Sheet types are links in one production chain
Sheets sold under different names are really different processing stages of the same steel. The chain runs: steel is hot-rolled (black sheet), its oxide scale is removed with acid (HRP), it is rolled again at room temperature to a thinner gauge (DKP / cold-rolled) and coated with zinc against corrosion (galvanized sheet). Optionally, factory paint is applied over the galvanizing (pre-painted sheet).
Comparison table
| Black sheet | HRP (pickled) sheet | DKP (cold-rolled) | Galvanized sheet | |
|---|---|---|---|---|
| Production | Hot-rolled | Hot-rolled + pickled, oiled | Cold-rolled, annealed | Zinc-coated (usually cold-rolled substrate) |
| Surface | Dark, scaled (oxidised) | Clean, matt grey | Smooth, bright | Zinc-coated, metallic grey |
| Thickness tolerance | Wide | Wide | Tight | Tight (per substrate) |
| Corrosion protection | None | Temporary oil only | Temporary oil only | Zinc coating (Z100–Z275) |
| Common standard | EN 10025 (e.g. S235JR) | EN 10111 (DD11…DD14) | EN 10130 (DC01…DC06) | EN 10346 (DX51D+Z…, S250GD+Z…) |
| Typical use | Thick structural parts, welded fabrication | Bending, pressing, chassis parts | Painted casings, panels, furniture, appliances | Outdoors, roofing, HVAC, damp areas |
What is black sheet?
Black sheet is hot-rolled sheet sold with the dark oxide (mill scale) layer from rolling, which gives it its colour. It is economical and is mostly used in thick sections, welded steel fabrication and where appearance does not matter. If it is to be painted, the scale must be removed by blasting.
What is HRP sheet?
HRP (pickled sheet) is hot-rolled sheet cleaned of scale in an acid bath and oiled. It is the same steel as black sheet; the difference is its clean surface, which makes it better for bending, pressing and painting. Grades DD11–DD14 are defined in EN 10111.
What is DKP sheet?
DKP is cold-rolled sheet made by rolling pickled hot-rolled sheet again at room temperature and annealing it. Its thickness is more precise and its surface smoother; it suits deep drawing and precise forming. Grades DC01–DC06 are in EN 10130. DKP has no coating; left unpainted in damp conditions it rusts quickly.
Galvanized sheet vs DKP
Galvanized sheet is largely made by coating a cold-rolled substrate similar to DKP with molten zinc on a continuous line. Mechanically they are close, but galvanized sheet carries its own corrosion protection, while DKP is unprotected unless painted. Galvanized sheet is preferred outdoors, in damp areas and where paint maintenance is difficult. For the definition and grade designation of galvanized sheet, see what is galvanized sheet.
What do grade codes like DX51D and S250GD mean?
In galvanized sheet, the first letters of the grade show its purpose. Grades starting with DX (DX51D, DX52D, DX53D, DX54D…) are for forming; higher numbers mean better deep-drawing ability. DX51D is the most common general-purpose grade. S…GD grades (S220GD, S250GD, S350GD…) are structural steels; the number is the minimum yield strength in MPa. +Z at the end denotes the zinc coating, followed by the coating mass (e.g. DX51D+Z275).
Which should I choose?
- Thick, welded structures to be painted later: black sheet or HRP.
- Precise, painted indoor casings: DKP.
- Outdoors, roofing, façades, HVAC, agriculture and damp areas: galvanized sheet; for colour, pre-painted sheet.
This article was prepared by the İpek Metal technical team. Contact us for values specific to your project.