Galvanizing residues 

Why do zinc residues form? 

Hot-dip galvanising is carried out in accordance with DIN EN ISO 1461, whilst grating is manufactured in accordance with DIN 24537 (with dimensional and shape tolerances in accordance with RAL-GZ 638). Whilst these standards require a surface finish suitable for the intended use, they do not specify any percentage limits for mesh openings. Due to physical factors, fine-mesh gratings (e.g. with a mesh size of 30/10 mm) are more prone to individual meshes becoming clogged with zinc flakes or thin zinc films when immersed in the zinc bath. Our specification provides a reliable and fair benchmark in this regard.

Details of standard galvanising (our quality specification)

For a standard order, goods falling within the following tolerances are considered technically sound and do not constitute a material defect: 

• At least 90 per cent of the total mesh area must be completely open. 
• A maximum of 2 per cent of all meshes may be completely closed. 
• A maximum of 3 meshes may be closed immediately adjacent to one another. 
• Functionality: Water drainage, air permeability, slip resistance and safe walkability must not be compromised under any circumstances. 
• Important: Loose, sharp-edged or breakable zinc projections are never permitted under any circumstances.

How testing is carried out: The testing and assessment procedure

The assessment is carried out visually in normal daylight and from a standard viewing distance (microscopic effects or purely colour deviations/dullness of the zinc coating are excluded).
To assess partial coverage, we use the transparent reference mesh model:

• Fully covered = 1.00
• Approx. 75 per cent covered = 0.75
  
• Half (50 per cent) covered = 0.50
  
• Approx. 25 per cent covered = 0.25

What does not constitute grounds for a complaint?

In accordance with technical standards, the following visual characteristics do not constitute grounds for a complaint:

• Colour variations, mattness, spotting or dark discolouration of the zinc coating.
  
• White rust caused by transport or storage when exposed to moisture.
  
• Zinc protrusions outside the opening area (provided this does not affect installability and there is no risk of injury).
  
• Dimensional and shape tolerances (the RAL-GZ 638 quality assurance standard applies here).
  

Complaints & efficient handling

In accordance with Section 377 of the German Commercial Code (HGB), the goods must be inspected immediately upon receipt. To ensure that any complaint can be dealt with quickly and efficiently, we require the following details from you:

1. Order or delivery
   note number
2. Item and exact mesh size (e.g. MW 30/10 mm)
   
3. Number of affected gratings (please specify the exact quantity)
   
4. Photo 1 (overview): The entire grating photographed
   vertically in daylight
5. Photo 2 (detail): The affected area with a folding rule or scale
   placed against it
6. Count: Brief description of the blocked or partially covered mesh openings in the test area
   

Following inspection, should a valid defect be found, you will receive a replacement or professional rectification from FeNau GmbH as soon as possible.