Hobson technical document
GEOMET Coating on Schnorr Safety Washers: Properties and Standards
A two-page Hobson technical sheet on the GEOMET coating offered on a select range of Schnorr safety washers, and by request on all Schnorr products. It explains what the coating is, its environmental and functional benefits, the standards it meets and how to order it.
What this covers
- What GEOMET is
- Environmental benefits
- International standards
- Functional benefits
- Coating thickness and corrosion resistance
- Ordering designation
For Structural Washer.
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- GEOMET is a water-based coating of zinc and aluminium flakes in metal oxides, cured at 300 to 315°C into an inorganic, matt silver coating. It was formerly known as DACROMET, before the chromium 6+ was removed.
- Chromium free: no hexavalent and no trivalent chromium.
- No acid pickling or electroplating in the process, so the coating process is free of hydrogen embrittlement.
- The aluminium flake removes the bimetallic cell most zinc coatings form against aluminium or steel. The coating is also solvent resistant, conductive and keeps its corrosion resistance after a 3 hour heat shock at 288°C.
- Two classes: Class A, 5 to 8 µm thick, more than 480 hours corrosion resistance; Class B, 8 to 10 µm, more than 720 hours. Order as GEOMET 321 A or GEOMET 321 B.
- GEOMET 321 meets EN ISO 10683, EN 13858 and ASTM F1136 for zinc flake coatings on fasteners and steel parts.
Who it helps: Engineers and buyers specifying a chromium-free coated safety washer, especially against aluminium or steel.
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This document is published by Hobson Engineering, who supply this range to us. We show it here in full so you can read it next to the product; the summary above is ours. Read it on this page or download the PDF. For the most current version, ask us.