Zinc Alloy Runner Scrap

Updated: 2026-07-20

Overview

Zinc alloy scrap, commonly known as 'zinc alloy runner scrap' or 'sprue scrap,' is a byproduct of die-casting and manufacturing processes. It consists of excess material from gates, runners, and rejected castings primarily composed of zinc alloys (often Zamak series). This material holds significant value in recycling due to zinc's infinite recyclability without quality degradation. In industrial contexts, this scrap is categorized as 'clean' or 'contaminated,' with the former commanding higher prices. The global zinc recycling market processes millions of tons annually, with Asia being a major hub for both generation and reprocessing of zinc alloy scrap.

Physical and Chemical Properties

Zinc alloy scrap typically exhibits a silver-gray metallic appearance with varying surface oxidation depending on storage conditions. The physical properties mirror those of virgin zinc alloys, including good castability, dimensional stability, and moderate strength. Common alloying elements like aluminum (3.5-4.3%) and copper (0-1%) influence the scrap's melting range and mechanical characteristics. Chemically, zinc alloys demonstrate excellent corrosion resistance in normal atmospheres but are reactive to strong acids and alkalis. The scrap's density ranges between 6.6-7.1 g/cm³, slightly lower than pure zinc due to alloying components. Thermal conductivity remains approximately 113 W/(m·K), making it valuable for heat dissipation applications.

Main Applications

The primary application of zinc alloy scrap is remelting for new die-cast components, achieving 70-90% energy savings compared to primary zinc production. Major end-use sectors include automotive parts (lock mechanisms, carburetor housings), hardware components (buckles, zippers), and electrical fittings (connectors, switchgear). Secondary applications include zinc dust production for anti-corrosion coatings and as an additive in brass manufacturing. Some high-purity zinc scrap enters the galvanizing industry after purification. The material's excellent fluidity when molten makes it particularly suitable for intricate die-cast designs with thin walls and complex geometries.

Safety and Storage

While zinc alloy scrap is generally stable, proper handling precautions are essential. Dust generated during processing may cause metal fume fever if inhaled, necessitating local exhaust ventilation and respiratory protection in work areas. The material should be stored away from moisture to prevent surface oxidation that could affect remelting efficiency. Fire safety measures should address zinc's relatively low melting point. Storage areas must be segregated from acids and strong oxidizers to prevent hazardous reactions. Containers should be clearly labeled with alloy composition details for safe downstream processing and to prevent accidental mixing with incompatible metals like magnesium.

B2B Procurement Guide

When sourcing zinc alloy scrap, buyers should prioritize suppliers who provide material analysis certificates detailing alloy composition (typically ASTM B240 standards). Key specifications to verify include aluminum content (3.8-4.3% for Zamak 3), copper limits (<1.25%), and maximum impurity levels (lead <0.005%, cadmium <0.004%). Purchase contracts should clearly define moisture content (ideally <0.5%), packaging requirements (bulk or palletized), and acceptable contamination levels (oil, paint, or other metals). Many buyers implement a quality-based pricing model with penalties for off-spec materials. Establishing long-term relationships with certified recyclers often yields more consistent quality than spot market purchases.