What is Dacromet Coating?

Why Do We Specify It For Our Garden Shed Screws?

When choosing metal fasteners like self-tapping screws, one important consideration is which protective coating to use for corrosion resistance and other performance factors.

Common options include

  • zinc galvanizing
  • nickel plating
  • dacromet coating

Of these, dacromet stands out as an optimal solution for several reasons.

Dacromet Self Tapping Screw

Dacromet coating has a metallic silver-gray appearance similar to zinc but slightly darker and more neutral in tone. The thin smooth layer uniformly covers the underlying screw substrate with a consistent dull sheen.

What is Dacromet?

Dacromet is a surface enhancement coating comprised of zinc and aluminium applied via a dry process. The zinc protects as a sacrificial anode while the aluminium oxidizes to create an impervious barrier against corrosion. Dacromet layers measure just 3-5 microns thick but offer excellent longevity and adaptability.

Corrosion Resistance

Exposure to moisture poses one of the largest threats to screws and fasteners. Dacromet coating provides superior resistance by both actively inhibiting rust and passively separating the substrate from oxidation sources. It withstands over 500 hours of salt spray testing with no red rust corrosion. Comparatively, galvanized coatings exhibit red rust in under 72 hours under beachside conditions.

Lubricity & Torque-Tension

The thin, dry dacromet deposition produces a smooth, low-friction surface. This allows self-tapping screws to drive into substrates easier with improved lubricity. In turn, dacromet coating sustains more consistent torque-tension performance. meaning the rotational resistance better correlates to clamp load. This ensures reliable connections without stripping or over-tightening. Galvanized and nickel-plated screws tend to demonstrate much greater variability in torque-tension relationship.

Ductility & Fatigue Strength

Unlike galvanized zinc layers, dacromet does not embrittle or make screws more prone to fatigue failure from bending stresses. Dacromet retains decent flexibility and fatigue limit like untreated steel, permitting use in dynamic applications. Furthermore, the ductile coating helps self-tapping screws conform to cross-sectional changes and irregular holes as they thread into a substrate. Brittle plating’s like nickel often crack or flake in these scenarios which damage the drive recess or threads.

Environmental Friendliness

The dry process dacromet method utilized today captures over 99.9% of any environmental byproducts for recycling. This marks a significant improvement over past wet bath procedures. Dacromet represents a much greener coating technology with low VOC emissions and energy consumption, especially compared to electroplated nickel. It also avoids utilization of dangerous chemicals associated with nickel plating.

Overall, dacromet coating outperforms galvanized zinc and nickel plating for self-tapping screw longevity and fastening performance. Its rust prevention, friction properties, fatigue life, and eco-friendly nature cement it as an optimal choice over more common plating’s. Engineers and manufacturers benefit from specifying dacromet-treated self-tappers where possible for superior behaviour in numerous construction applications.

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