Scrap Metal Composition Testing: Methods, Standards, and Industrial Applications

Scrap metal composition testing delivers accurate elemental analysis of recycled ferrous and non-ferrous materials, supporting reliable grading, valuation, and melt-charge control across the recycling and metallurgical industries. Accredited third-party laboratories apply techniques such as optical emission spectrometry, X-ray fluorescence, and ICP analysis in accordance with ISO, ASTM, EN, JIS, and GB standards. This guide explains the key sample types, testing items, analytical methods, and practical applications of scrap metal composition analysis.

Technical Overview

Scrap metal is one of the most important secondary raw materials in modern manufacturing, and its commercial value, processability, and safety depend directly on its chemical composition. Scrap metal composition testing is the systematic analytical process of quantifying the elemental makeup of recycled metallic materials, detecting undesirable tramp elements, screening for hazardous and radioactive contaminants, and verifying conformity with purchase specifications, industry standards, and environmental regulations.

Unlike primary metal products, recycled materials are inherently heterogeneous. Mixed grades, alloy families, coatings, paints, oils, rubber attachments, and non-metallic inclusions are all commonly encountered. As a result, representative sampling and preparation are as critical as the measurement itself. Modern practice combines rapid on-site screening techniques with laboratory-grade quantitative methods, allowing recyclers, smelters, traders, and regulators to make defensible decisions based on certified data from accredited third-party laboratories operating under ISO/IEC 17025 quality systems.

Testing Samples

Ferrous Scrap

Ferrous materials represent the largest volume of traded scrap worldwide. Typical submitted samples include:

• Carbon steel scrap: heavy melting steel, shredded steel, plate and structural scrap, and rebar
• Alloy steel scrap: chromium-molybdenum grades, tool steels, and spring steels
• Stainless steel scrap: austenitic grades such as 304 and 316, ferritic and duplex grades
• Cast iron and pig iron: gray iron, ductile iron, and foundry returns
• Machining residues: turnings, borings, and swarf with varying degrees of contamination

Non-Ferrous Scrap

Non-ferrous scrap typically carries a significantly higher unit value, making precise elemental characterization essential for pricing:

• Aluminum scrap: used beverage cans, cast alloy scrap, extrusions, and mixed alloys
• Copper scrap: bright wire, copper clad, brass, bronze, and radiators
• Lead scrap: batteries, sheet lead, cable sheathing, and remelted lead ingots
• Zinc, tin, nickel, and magnesium scrap in bulk or processed forms
• Remelted products: sows, ingots, billets, and T-bars produced by secondary smelters

Specialty and Mixed Materials

Complex material streams require extended analytical scope:

• Superalloy and titanium scrap from aerospace and energy sectors
• Electronic scrap and precious-metal-bearing materials
• Slags, drosses, flue dusts, and mill scale for metal recovery assessment
• Mixed loads of unknown alloy families requiring sorting and identification

Testing Items

Testing programs are tailored to the alloy system and commercial purpose, but typically cover the following categories:

• Major alloying elements: C, Si, Mn, P, S, Cr, Ni, Mo, Cu, V, Ti, W, Al, Mg, Zn, Pb, Sn, and Fe depending on the material class
• Tramp and residual elements: As, Bi, Sb, Se, Te, and Sn, which degrade ductility and hot workability even at ppm levels
• Hazardous and regulated substances: Pb, Cd, Hg, Cr(VI), and brominated compounds relevant to RoHS-type restrictions and waste classification
• Radiological screening: detection of artificial gamma emitters such as Cs-137 and Co-60 in imported or collected scrap
• Dissolved gases in high-value alloys: oxygen, nitrogen, and hydrogen content
• Valuable metal assays: Au, Ag, Pt, Pd, and Cu in electronic and precious metal scrap

Testing Methods

Spark Discharge Optical Emission Spectrometry (SD-OES)

Spark OES is the reference technique for routine quantitative analysis of metallic samples. A spark discharge vaporizes the sample surface, and the emitted characteristic wavelengths are used to quantify elements simultaneously from carbon to heavy metals. Standardized methods include ASTM E415 for carbon and low-alloy steels, ASTM E1086 for austenitic stainless steel, GB/T 4336, and GB/T 11170. Solid samples require milling or grinding to a flat, clean analytical surface.

X-Ray Fluorescence Spectrometry (XRF)

XRF enables rapid, largely non-destructive elemental screening for elements from magnesium to uranium. Benchtop wavelength-dispersive systems provide high-precision grade confirmation, while handheld instruments following the general practice of ASTM E1621 support fast incoming inspection and alloy sorting at yards, ports, and production lines. XRF cannot measure light elements such as carbon, which is why it is frequently paired with combustion or OES methods for full characterization of steels.

Inductively Coupled Plasma Techniques (ICP-OES and ICP-MS)

After acid digestion of drillings or milled portions, ICP-OES delivers multi-element quantification with wide linear range, while ICP-MS extends detection limits into the ppb region for trace and tramp elements. These techniques follow practices such as ASTM E1479 and are indispensable for verifying residual element limits, compliance screening of restricted substances, and precious metal assays in complex matrices.

Combustion Infrared and Inert Gas Fusion Analysis

Carbon and sulfur are determined by high-frequency combustion with infrared detection, while oxygen, nitrogen, and hydrogen are measured by inert gas fusion, commonly under ASTM E1019 and GB/T 20123. These parameters control weldability, toughness, and embrittlement behavior in recycled steel and specialty alloys.

Laser-Induced Breakdown Spectroscopy (LIBS)

LIBS uses a focused laser pulse to generate a micro-plasma and is increasingly applied to high-speed sorting of aluminum and mixed alloy streams, including light element measurement, complementing handheld XRF in automated recycling facilities.

Radiometric Screening and Gamma Spectrometry

Radiation portal monitors and handheld dose-rate instruments provide initial clearance of scrap loads, while laboratory gamma spectrometry identifies specific radionuclides when elevated readings are confirmed. Import controls reference environmental protection standards such as the GB 16487 series and applicable national radiation protection regulations.

Applications

Scrap metal composition testing supports decision-making across the entire secondary metals value chain:

• Trading and valuation: element-based pricing, premium and penalty calculations, and grade verification for buyers and sellers
• Steelworks and foundries: melt-charge design, tramp element control, and prevention of off-specification heats caused by contaminated scrap
• Secondary smelters: charge blending for aluminum, copper, lead, and zinc recycling operations
• Customs and regulatory inspection: conformity assessment of imported scrap against environmental and radioactivity limits
• Alloy identification and positive material identification (PMI) for aerospace, automotive, and construction supply chains
• Dispute resolution and due diligence: independent certified data for arbitration, insurance claims, and transaction audits
• Waste classification: distinguishing recyclable scrap from hazardous waste for lawful handling and disposal

FAQ

How much sample is required for analysis?

For spark OES, a solid piece of at least several grams with a flat surface greater than the spark stand aperture is needed. For wet-chemical ICP methods, 5 to 20 grams of clean drillings or millings are typically sufficient, while heterogeneous streams such as shredded scrap requireIncremented multi-increment sampling to ensure representativeness.

How long does scrap metal composition testing take?

Standard elemental analysis by OES or XRF is usually completed within one to three working days after sample preparation. Tests involving digestion and ICP, trace-level determinations, or radioisotope identification may require three to seven working days depending on scope.

Can mixed or heavily contaminated scrap be tested?

Yes. Coated, painted, oily, or mixed-material samples are first cleaned, sorted, and prepared using standardized procedures. Sampling guidance such as ISO 14284 for steels, ASTM E1806, and ASTM E255 for copper alloys is applied to minimize bias from heterogeneity.

Is radioactive screening included in composition testing?

Radiological screening is a distinct but frequently bundled service. Given the severe safety and legal consequences of orphan sources entering a melt, accredited third-party laboratories strongly recommend radiation clearance testing alongside elemental analysis, particularly for imported or mixed-origin scrap.

Which standards govern the results?

Depending on material and element, methods are performed according to ASTM, ISO, EN, JIS, and GB standards, for example ASTM E415 and GB/T 4336 for steels, GB/T 20975 for aluminum alloys, and GB/T 5121 for copper alloys. Test reports from ISO/IEC 17025-accredited laboratories provide the highest level of international acceptance.

Can precious metals in electronic scrap be assayed?

Yes. Gold, silver, and platinum-group metals are quantified using fire assay, ICP-OES, and ICP-MS procedures after controlled sampling and digestion, providing the basis for settlement between recyclers and smelters.