Chemical Property Determination of Non-ferrous Metals: Composition Analysis and Corrosion Testing Gu

Chemical property determination of non-ferrous metals is a critical laboratory discipline that verifies elemental composition, impurity levels, gas contents, and corrosion resistance of materials such as aluminum, copper, titanium, nickel, zinc, and precious metal alloys. This guide explains the key testing samples, testing items, standardized methods, and industrial applications involved, helping manufacturers, suppliers, and quality engineers select the right testing approach in accredited third-party laboratories.

Technical Overview

Non-ferrous metals and alloys—including aluminum, magnesium, titanium, copper, zinc, lead, nickel, tin, cobalt, tungsten, molybdenum, precious metals, and rare earth metals—are essential engineering materials in aerospace, electronics, energy, transportation, and construction. Because the service performance of these materials is governed by their chemical characteristics, chemical property determination has become a fundamental part of material qualification, incoming inspection, and failure analysis.

Chemical property determination covers two complementary areas. The first is quantitative chemical composition analysis, which measures major alloying elements, trace alloying additions, and harmful impurities such as lead, bismuth, cadmium, arsenic, and antimony. The second is chemical behavior testing, which evaluates corrosion resistance, oxidation resistance, intergranular corrosion susceptibility, and chemical stability in service environments. Together, these evaluations confirm conformity with material specifications issued by ISO, ASTM, EN, JIS, and GB standards organizations and support reliable material selection.

Testing Samples

Accredited third-party laboratories accept a wide variety of non-ferrous metal samples for chemical property determination. Typical sample categories include:

Light Metal Alloys

Aluminum and aluminum alloys (1xxx to 7xxx series), magnesium alloys (AZ and AM series), and titanium alloys (commercially pure titanium, Ti-6Al-4V and other grades), supplied as ingots, sheets, plates, extrusions, tubes, rods, wires, castings, forgings, or powders.

Heavy Non-ferrous Metals and Alloys

Copper and copper alloys including brasses, bronzes, and cupronickels; refined copper cathodes; zinc and zinc alloys for die casting and galvanizing; lead and lead alloys; tin, solder alloys; nickel and nickel-based alloys; and cobalt alloys.

Precious Metals and Refractory Metals

Gold, silver, platinum, palladium and platinum-group alloys, jewelry and bonding wires, tungsten and molybdenum products, tantalum and niobium materials, and rare earth metals and compounds.

Special Sample Forms

Surface coatings and plated layers, welds and brazed joints, metal powders, turnings and drillings, corrosion products, and small electronic components can all be characterized using appropriately scaled sampling and micro-analytical techniques.

Testing Items

Common testing items for chemical property determination of non-ferrous metals include:

• Major element composition: quantification of primary alloying elements such as Cu, Zn, Al, Mg, Si, Mn, Ni, Sn, and Cr.
• Trace and impurity elements: determination of Fe, Pb, Cd, As, Sb, Bi, P, S, and other residual elements at ppm levels.
• Gas element analysis: oxygen, nitrogen, and hydrogen contents, particularly critical for titanium, zirconium, and refractory metals where interstitial gases control ductility and embrittlement behavior.
• Carbon and sulfur determination in non-ferrous alloys and metal powders.
• Corrosion resistance testing: neutral salt spray, acetic acid salt spray, and copper-accelerated salt spray exposure.
• Intergranular corrosion susceptibility of aluminum and copper alloys.
• Pitting and crevice corrosion evaluation, galvanic corrosion behavior, and immersion corrosion rate measurement.
• Oxidation resistance and high-temperature chemical stability.
• Chemical composition and thickness verification of conversion coatings and electroplated layers.
• Dissolution behavior and chemical compatibility in acids, alkalis, and process media.

Testing Methods

Testing methods are selected according to the element of interest, the required detection limit, the sample form, and the governing product specification.

Atomic Emission Spectrometry

Spark source optical emission spectrometry (Spark OES) enables rapid quantitative bulk analysis of solid metallic samples. ASTM E1251 covers the analysis of aluminum and aluminum alloys by Spark OES, while ASTM E478 provides classical procedures for copper alloys. Inductively coupled plasma optical emission spectrometry (ICP-OES) and ICP mass spectrometry (ICP-MS) provide multi-element determination with detection limits down to sub-ppb levels after acid digestion of the sample.

X-ray Fluorescence and Surface Analysis

X-ray fluorescence (XRF) spectrometry offers non-destructive elemental screening of alloys, and coating thickness measurement by X-ray spectrometry is standardized in ASTM B568 and ISO 3497. Glow discharge optical emission spectrometry (ISO 14707) provides depth-profiling of surface layers, while X-ray photoelectron spectroscopy and Auger electron spectroscopy (ISO 18118) characterize surface chemistry, oxidation states, and passive films.

Classical Wet Chemical Analysis

Gravimetric, titrimetric, colorimetric, and electrolytic methods remain reference techniques for certifying reference materials and arbitrating disputed results. These procedures deliver high accuracy for major constituents such as copper in brass, nickel in alloys, and silver in precious metal materials. National method series such as GB/T 20975 for aluminum, GB/T 5121 for copper alloys, and GB/T 13748 for magnesium alloys document detailed wet-chemical and instrumental procedures.

Combustion and Inert Gas Fusion Analysis

Corrosion and Chemical Behavior Testing

Salt spray exposure is performed to ASTM B117, ISO 9227, and GB/T 10125 to assess atmospheric corrosion resistance. Immersion corrosion rates are measured following ASTM G31, galvanic corrosion behavior is evaluated per ASTM G71, and intergranular corrosion of aluminum alloys is assessed by ASTM G110 and ISO 11846. Electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy, quantify pitting propensity and passive film stability.

Applications

Chemical property determination of non-ferrous metals supports quality control and material qualification across many industries:

• Aerospace: certification of titanium and high-strength aluminum alloys where oxygen, hydrogen, and trace impurities directly affect flight safety.
• Automotive: verification of aluminum and magnesium castings, copper radiators, and battery materials for electrified vehicles.
• Electronics and semiconductors: purity confirmation of copper, solder alloys, bonding wires, and precious metal contacts.
• Marine and chemical processing: corrosion resistance qualification of cupronickel heat exchanger tubes and nickel alloys.
• Construction: compliance testing of aluminum profiles, copper plumbing tubes, and zinc coatings.
• Medical devices: chemical verification of implant-grade titanium meeting stringent impurity limits.
• New energy: elemental analysis of nickel, cobalt, and rare earth materials for batteries and permanent magnets.
• Recycling and metal trading: grade classification and valuation of scrap, ingots, and secondary alloys.

FAQ

What is the difference between chemical composition analysis and chemical property testing?

Chemical composition analysis quantifies which elements are present and in what amounts, whereas chemical property testing evaluates how the material behaves chemically in service, such as its resistance to salt spray corrosion, oxidation, or intergranular attack. A complete characterization program typically combines both.

How are trace impurities in non-ferrous metals measured?

Trace elements are measured mainly by ICP-OES, ICP-MS, graphite furnace atomic absorption spectrometry, and Spark OES, with detection limits ranging from ppm to sub-ppb depending on the technique, matrix, and sample preparation method.

What sample size and preparation are required?

Spark OES generally requires a flat solid disc or block of at least 20 mm across; wet chemical and ICP methods typically need 0.2 to 2 grams of clean drillings or cut pieces; inert gas fusion analysis uses approximately 0.1 to 1 gram. Samples must be free of oil, paint, plating, and oxidation unless the coating itself is the object of the test.

Which standards govern the testing?

Depending on the material and property, common references include ASTM E1251, ASTM E478, ASTM E1019, ASTM E1409, ASTM E1447, ASTM B117, ASTM G31, ASTM G71, ASTM G110, ISO 9227, ISO 11846, ISO 14707, and the corresponding GB/T method series. The applicable standard is dictated by the product specification or the agreement between buyer and supplier.

How long does chemical property determination take?

Routine spectroscopic composition analysis of a metallic sample is often completed within two to five working days. Corrosion tests such as salt spray exposure are schedule-driven and may require from 24 hours to several weeks depending on the specified exposure duration.

Why is gas element analysis important for titanium?

Oxygen, nitrogen, and hydrogen occupy interstitial sites in the titanium lattice and strongly reduce ductility and fracture toughness. Excessive hydrogen can cause hydride embrittlement, so ASTM E1409 and ASTM E1447 determinations are mandatory acceptance tests for most titanium product specifications.