In scrap trading, contamination covers everything in a lot that is not the agreed aluminium grade: free iron and steel, iron inserts and screws, brass, copper, zinc die castings, lead, plastic, rubber, glass, paper, paint, dirt, oil, coolant and water. ISRI-style specifications state the maximum allowed for each grade, and buyers deduct or reject lots that exceed it.
Why it matters when buying
- Contamination reduces recovery, so a lot with 5% attached iron is worth less than its gross weight suggests.
- Moisture and trapped liquids are dangerous: water in a charge can cause violent steam explosions in molten metal. Insist on dry material.
- Elements such as iron, zinc and magnesium carried in by mixed scrap can push a melt out of specification for alloys like ADC12.
- Agree on inspection, sampling and deduction rules before loading, and photograph the lot.
Notes
Oily turnings are often dried or de-oiled before melting; coated scrap such as UBC is de-coated. The scrap grades guide lists typical limits by grade, and the AluminumBazaar desk can arrange inspection before dispatch.