Hard chrome coating has been one of the most proven surface solutions for extrusion screws in plastics and rubber processing for decades. Through the electrolytic deposition of a highly durable chrome layer, an extremely wear-resistant, corrosion-resistant, and low-friction surface is created — specifically designed for demanding extrusion processes.
The smooth and hard chrome surface reduces friction, minimizes material adhesion, and reliably protects the screw against abrasive wear and chemical attack. This extends service life, reduces cleaning intervals, and significantly improves process stability.
Advantages of Chrome Coating
- Very high surface hardness of approx. 68–72 HRC
- Excellent wear and abrasion resistance
- Extremely smooth surface with low coefficient of friction
- Reduced material build-up and improved non-stick properties
- High corrosion resistance against aggressive media
- No distortion or dimensional change of components
- Good temperature resistance
- Improved cleanability of the screw surface
- Extended service life of the extrusion screw
Due to its low surface roughness, hard chrome is particularly suitable for processing sensitive or highly adhesive polymers. At the same time, the hard chrome layer offers excellent resistance against mineral-filled and glass fiber reinforced compounds.
Technical Characteristics
In the hard chrome plating process, a chrome layer is electrolytically deposited onto the screw surface. The coating is characterized by high hardness, low friction, and excellent chemical stability.
Typical properties:
- Hardness: approx. 68–72 HRC
- Coating thickness: typically 20–100 µm
- Very low coefficient of friction
- High dimensional accuracy
- Excellent adhesion to the base material
- Temperature and oxidation resistant
- Diffusion-resistant protective effect
Hard chrome plating is suitable both for new extrusion screws and for the refurbishment and repair of worn screws.
Applications in Plastics and Rubber Processing
Chrome-coated extrusion screws are commonly used for:
- PVC extrusion
- PE and PP processing
- Engineering plastics
- Glass fiber reinforced compounds
- Rubber and elastomer processing
- Adhesive or abrasive materials
- Recycling applications with increased wear requirements
The hard and low-friction surface reduces material deposits and improves melt conveying behavior — especially in demanding formulations and high-output extrusion processes.
Advantages Compared to Uncoated Surfaces
Compared to untreated or only nitrided screws, chrome coating offers significantly higher surface hardness as well as improved sliding and non-stick properties. As a result, friction, material adhesion, and wear are substantially reduced. In addition, the smooth chrome surface simplifies cleaning and minimizes production downtime.