ZI-101 Metals

(V 2018-07-16)


Galvanized Steel Strips (Hot dip galvanized / sendzimir galvanized)

DX 51 D × Z 140 MA according to DIN EN 10 142 (Zinc coating thickness ≈ 10 µm per side).
DX 51 D × Z 275 MA according to DIN EN 10 142 (Zinc coating thickness ≈ 20 µm per side), upon request.

METU-FORM Straight Ducts made of Galvanized Steel

Straight circular ducts longer than 1500 mm for diameters from 500 to 1000 mm are only available upon request: Steel suppliers can guarantee neither the availability nor the surface appearance / quality of the galvanized steel required for the manufacture of straight METU-FORM ducts longer than 1500 mm for diameters ranging from 500 to 1000 mm. These products are therefore considered as "special" (*) and are only available upon request. The appearance of the surface can vary and is no reason for claims. Thank you for considering the above should you wish to place an order. 

(*) Orders of special products cannot be amended or cancelled once placed and the goods cannot be returned.

Temperature Resistance: (Zinc coating Z: 140 to 275 g/m2)

Up to max. 200°C on a sustained basis. When the zinc coating is subject to temperatures above 200°C on a sustained basis, the so called “Kirkendal” voids between the steel and the zinc layer might occur, leading to the flaking of the zinc surface.

Electro-galvanized Parts

Some parts, such as bolts, nuts, springs, G-clamps, drive-clamps and corner pieces can only be electro galvanized. The zinc layer thickness varies between 5 and 10 µm on each face, and the temperature resistance is limited to a maximum of 80°C. Please take into consideration the lower corrosion resistance.

Corrosion and Temperature Resistances

The below information is valid for all products described as being made of galvanized steel.

The edges of cut are not galvanized. In a relatively humid environment corrosion might occur on sheet metal thickness of 1,2 mm and above, and already on 1.0 mm sheet metal thickness in very humid environments.

The sheet metal is dip galvanized and the zinc coating relatively important. Additional parts such as corner pieces, installation elements, nuts and bolts, rivets, curved joining clip bolts, shells, and others are electro galvanized. The zinc coating is between 0,008 and 0,010 mm thick, making these parts less resistant to corrosion.

Also to be noted is that the zinc coating might become damaged through assembly and/or other operations such as spot welding, welding, the use of rivets and self-piercing screws or bolts.

The corrosion resistance also depends on the temperature. The zinc coatings can be different depending on the product components (i.e. hot dip galvanized vs. electro galvanized). Higher temperatures can have a negative influence on the coatings and even destroy them. Above 200°C is the corrosion resistance of hot dip galvanized slit stripes no longer guaranteed. Above 80°C the corrosion resistance of electro-galvanized parts (such as bolts and nuts) can be negatively affected, and there is no corrosion resistance above 120°C.

Electro-galvanic Corrosion

It is important to check the compatibility of the various materials in order to avoid corrosion. The potential electro-galvanic corrosion (which appears when different materials are put in contact) must be assessed.

See also DIN EN 12944

Cathodic: protected when in contact with a less noble metal
Anodic: corrodes first when in contact with a nobler metal


Zinc Coated Surface

The appearance of the zinc surface can vary from one product to the other, since the material is not purchased by a unique supplier, and also because the deliveries from a same supplier can differ in time. For these reasons, we are not able to guarantee a constant zinc coating appearance.

Stainless Steel

Stainless steel is defined as a steel alloy with a minimum of 11,5% chromium content. This chromium part forms a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal‘s internal structure. The stainless steel might discolor when heated (i.e. along the welds).

Stainless Steel V2A

V2A refers to the below mentioned quality or a comparable stainless steel within the same category.
Material Nr. 1,4301 / X 5 CrNi 18-10 (DIN EN 10 088-2, USA: ASTM 304).
Surface: Matt = 2B (III C), Shiny = 2R (III D).
Maximum Operating Temp.: 300°C (temporarily: 450°C). Data also depend on the gasket and the flow medium.

Food and pharmaceutical industries, chemical equipment. V2A is not suitable for swimming pool applications, as this material does not resist to chloride concentrations above 150-200 mg/l.

Stainless Steel V4A

V4A usually refers to the stainless steel 1.4404 (ASTM 316L), alternatively the 1.4571 (ASTM 316Ti) or a comparable quality within the same category.

Maximum Operating Temp.: 300°C (temporarily:450°C). Data also depend on the gasket and the flow medium.

Higher resistance against corrosion.

Assembly Instructions for Products made of Stainless Steel

A lubricating, anti-seize compound for stainless steel parts (i.e. TECCEM AHT415) should be used on stainless steel nuts and bolts. The tightening should be carried out carefully and by hand.


The appearance of the stainless steel surface can vary from one product to the other, since the material is not purchased by a sole supplier, and also because the deliveries from a same supplier can vary in time. A constant appearance can therefore not be guaranteed.


There is usually a 10%thickness tolerance for galvanized steel, stainless steel and aluminum.  These tolerances can also affect the weight of the products.

Work Safety

Please be aware that the edges of products made of stainless steel can be much sharper than the ones made of galvanized steel. We therefore recommend to always use protective gloves when handling our products.

Protective Foil

The stainless steel material comes with a self-adhesive protective foil, which also facilitates its processing.


Material: Al Mg3 (EN AW-5754)
Material Ref.: DIN 3.3535
Hardness: H111 (soft), and eventually H22 (medium hardness) /H32 (DIN G22)
Maximum Operating Temp.: 200°C ( ≈ 10 hrs). Data also depend on the gasket and the flow medium.
Melting Point:  ≈ 660 °C

Cooper (1235-0012)

Material: E-Cu (DIN 1787 / 40500)
Hardness: F25 (medium hardness, upper range)
Maximum Operating Temp.: +200°C. Data also depend on the gasket and the flow medium.
Melting Point: ≈ 1000 °C


Material: 2.0401
Coating: Nickel-faced

Aluminum Access Doors

Bolts, nuts and springs cannot be made of aluminum. This is why, on the aluminum access doors versions, these parts are made of stainless steel V2A.

Nickel-faced Parts (ST Drain Fittings)

The main reason for having nickel-faced parts is the corrosion resistance. By chromium plating, a nickel coating serves as an intermediate layer. The corrosion resistance of nickel-faced parts is therefore 25% lower than the one of chromium plated parts.

METU-FORM Welding Methods

Laser-welding for both galvanized and stainless steel.
Fittings in Galvanized steel.: Laser and Wolfram-Inertgas (WIG) / CUZI brazing.
Fittings in Stainless Steel V2A (304):  Laser and Wolfram-Inertgas (WIG) welds.


AISI American Iron and Steel Institute
SAE Society of Automotive Engineers
ASTM Amercan Society for Testing and Materials


Important Notice

The present additional information have been compiled carefully. They are only indications intended to provide counsel. They are the result of internal tests and information provided by our suppliers. There is no guarantee for completeness and accuracy. More precise information can only be made available through focused tests on a case by case basis. The provided indications do not discharge the user from conducting his own tests. Please make sure that the product is suitable for the intended use. Changes, errors and omissions excepted. Free translation: the German version prevails.

Galvanized Steel


METU-FORM Ducts, Fittings and Connections made of Stainless Steel.