Galvanized tubes

We offer a wide range of electrolytically zinc coated tubes for hydraulic and pneumatic circuit within the following parameters:

Dimensions of zinc coated tubes

OUTER DIAMETER (OD)4.0 - 42.0 mm
WALL THICKNESS (WT)1.0 - 4.0 mm

EN 10305-4;
DIN 2391; 2445-2
STN / ČSN 42 6711, 42 6712;
See tube sizes acc. to European standards

Tolerances of zinc coated tubes

- tolerances of the outside diameter:
diameter between 4 - 30 mm
diameter between 32 - 38 mm
diameter up to 42 mm
±0,08 mm
±0,15 mm
±0,20 mm
- tolerances of the inside diameter are according to EN 10305-4
- tolerance of the wall thickness ± 10%

Steel grades of tubes for hydraulic and pneumatic lines

EN 10305-4E235; E355
Marking system for steel grades according to EN
Chemical composition and mechanical properties of other possible steel grades acc. to EN, DIN, UNI, BS, NF-A, ASTM, JIS

Galvanized tubes

Surface condition of zinc coated tubes

First layerelectrolitically leached zinc (Zn) – acts as anode and in a corrosive environment it corrodes first and the base metal is cathodically protected against corrosion. The zinc layer thickness may be in the range of 5 to 30 micrometers (µm).
Second layer based on the valency of used chrome is called either: passivation or chromating. For chromating in the past the Cr+6 salts were used. Nowadays the term chromating is no longer used, but passivation, or based on the number of chromites (salts Cr3+) we are talking about chromiting.
Third layerfor the overall increase of coating resistance, we use as the last layer the layer of organic substances on the Si base that stabilizes the chrome layer. This process is called impregnation or sealing.
Surface condition of zinc coated tubes

Zeleziarne Podbrezova offers the following:
- zinc layer thickness of 10 micrometers (µm),
- strong second layer passivation that has a rainbow tint.
- last layer - sealed surface.

Allowable pressure for hydraulic and pneumatic lines

The highest allowable pressure for hydraulic and pneumatic lines in relationship to steel and tube testing. Calculation was done according to DIN 2413.
Steel 37.4 (E235) without specific testing according to 3.1.B (3.1)
Steel 37.4 (E235) with specific testing according to 3.1.B (3.1)
Steel 52.4 (E355) without specific testing according to 3.1.B (3.1)
Steel 52.4 (E355) with specific testing according to 3.1.B (3.1)



Length of zinc coated tubes

diameter 4 - 16 mm 6000 + 100 mm
diameter 18 - 426000 + 50 mm

Zinc coated tubes ends

The ends are vertical to the longitudinal axis and are without burrs. Ends of the tubes are smooth and are enclosed by plastic plugs
tubes capped with plastic caps ends of seamless pipes

Marking of zinc coated tubes

(a) Marking of metallic zinc coatings as it is described in DIN 50979.
- thin passivation (transparent) is colorless or slightly rainbow color. It is marked as A,
- strong passivation (rainbow – iris) it has a rainbow tint. It is marked as C,
- surface without sealing - there is no code. A sealed surface has T2 code.
Example of surface marking Fe / Zn8 / A / T2
(it means – steel, zinc 8 micrometers, transparent passivation, with sealing)
Tube bundles are marked by tags.

Marking of zinc coated tubes

Packaging of zinc coated tubes

Tube are supplied in packages with a circular or hexagonal outline with maximum weight of 2 000 kg

Tubes testing and coat resistence testing

Non specific or specifific testing.flattening test or drift expanding test
leak tightness test (NDT)
  • eddy current (STN 01 5054, PRP 02-74, SEP 1925, ASTM E 309, EN 10246-3 Gr.E3),
  • stray flux (STN 01 5047, ČSN 01 5047, SEP 1913, ASTM E 570, EN 10246-5 Gr.F3),
  • ultrasound (STN 01 5028, ČSN 01 5028, SEP 1915, ASTM E 213, EN 10246-7 Gr.U3),
Other tests according to standard.

Salt Spray (Fog) - ISO 9227
Minimum Corrosion Resistance [hours]
Type of protection
Zinc layer
EN 10239
ŽP achieved
Blue Passivating (bright)
HRI Silver Passivating

Certified test reports of zinc coated tubes

EN 10204 2.2 nonspecified testing (only mandatory tests),
3.1 specific testing,
3.2 after agreement .

Straightness ofzinc coated tubes

The allowable straightness for the whole length of the tube is 0.0015 multiple of the tube length, allowed straightness of one meter is 3 milimeters.

Delivery condition of zinc coated tubes

Tubes are delivered as cold drawn and normalized NBK (acc. to DIN standard), +N (acc. to EN standard), N (acc. to ASTM standard). Overview of other conditions can be found here. Coarseness of the outer and inner surface (starting with 15 mm of the inside diameter) is Ra <= 4 micrometers (0.004mm).

Galvanized tubes - electrolytically zinc coatedGalvanized tubesGalvanized tubes - electrolytically zinc coated tubes for hydraulic and pneumatic circuit