Aluminum Processing Industry Glossary

This glossary is written for both design/engineering and procurement audiences, in a bilingual quick-reference format, helping you quickly align concepts and parameters during material selection, drawing release, process review, RFQ, and acceptance. The values cited are common industry ranges for engineering communication only; actual requirements are governed by drawings, contracts, or mutually agreed technical specifications (as of 2025-10-22).— We suggest bookmarking this article and, during requirements preparation, checking it together with “Drawing Notes/Inspection Methods/Consistency Control.”

Alloys and Tempers (Temper)

• 6061 (Aluminum 6061)

• Definition: Heat-treatable aluminum alloy with a balanced combination of strength, machinability, and weldability; widely used for structural parts.

• Typical properties: T6 yield about 240–276 MPa, tensile about 310–350 MPa (subject to the Mill Test Certificate, MTC).

• Design/manufacturing tips: Suitable for anodizing; for deep cavities/thin walls, pay attention to distortion control and fixturing strategy.

• Purchasing/quality tips: Confirm temper (T6/T651); T651 (stretch stress-relieved) improves stability for thick plate/large parts. 

• 6063 (Aluminum 6063)

• Definition: Better extrudability and decorative surface finish; lower strength than 6061; common for profiles and architectural parts.

• Design/manufacturing tips: Good for anodized, dyed appearance parts; uniform thickness and generous radii help surface consistency.

• Purchasing/quality tips: Profile tolerances and die consistency at the supplier drive yield; request and approve samples early.

• 7075 (Aluminum 7075)

• Definition: High-strength aluminum (commonly T6/T73), widely used in aerospace structures; poor weldability.

• Design/manufacturing tips: Hard anodizing is possible, but uniformity and dyeability are inferior to 6xxx series; prototype for critical cosmetics.

• Purchasing/quality tips: Specify temper and mechanical acceptance criteria; set realistic expectations for anodic color consistency.

• 5052 (Aluminum 5052)

• Definition: Non-heat-treatable (Mg series), corrosion-resistant and weldable; common in sheet-metal enclosures and marine environments (e.g., H32).

• Design/manufacturing tips: Evaluate bend springback and minimum inside radius by thickness and grain direction.

• Purchasing/quality tips: Define base material spec, rolling direction, and surface grade to avoid mix-ups.

• T6 / T651 / T351 / H32 (Temper Codes)

• T6: Solution heat-treated + artificially aged;

• T651: T6 plus stretch stress relief;

• T351: Solution treated, stress-relieved by stretching + naturally aged;

• H32: Strain-hardened and then stabilized (partially annealed) to the specified strength.

• Definitions:

• Design/manufacturing tips: Tempers with “51/52/54” generally have lower residual stress, aiding dimensional stability.

• Purchasing/quality tips: At ordering and incoming inspection, verify temper marking, heat lot, and MTC.

Surface Finishing and Anodizing

• Anodizing types (MIL-PRF-8625 Types & Classes)

• Type I/IB: Chromic acid anodize; Type IC: non-chrome alternative;

• Type II/IIB: Sulfuric acid anodize (dyeable; IIB is a thin-film alternative);

• Type III: Hard anodize (usually low-temperature sulfuric system; wear-resistant thick film);

• Class 1 (undyed/natural), Class 2 (dyed).

• Definitions:

• Typical thickness ranges: Type I approx. 0.5–2.5 μm; Type II approx. 5–25 μm; Type III approx. 25–50+ μm (follow drawing/process agreement). A concise overview of types and classes is provided by the Aluminum Anodizers Council’s summary of the military spec (2019) Anodizing.org on MIL-A/MIL-PRF-8625.

• Design/manufacturing tips: Specify “Type/Class/thickness/sealing/color”; for appearance parts, create and file a color sample card in advance.

• Purchasing/quality tips: Cross-lot shade variation risk is high; lock to the same subcontract line and process window.

• Anodic coating thickness measurement (Coating Thickness Measurement)

• Definition: Eddy-current (non-destructive) and cross-sectional microscopy (destructive) are the two common measurement methods.

• Standards reference: On the shop floor, eddy-current per ASTM B244-09(2021) is common; the corresponding international standard is ISO 2360 (non-conductive coatings on non-magnetic conductive substrates). When specifying or communicating terms, cite the standard name, e.g., “measure per ASTM B244/ISO 2360.”

• Design/manufacturing tips: Rough surfaces and geometry affect eddy-current readings; calibrate with standards; for arbitration, use cross-sectional microscopy (e.g., ISO 1463).

• Purchasing/quality tips: Fix the measurement method and tolerance in the drawing or technical agreement to avoid “different method, different decision.”

Tolerances and Geometric Dimensioning (GD&T)

• General tolerances (ISO 2768-1 / GB/T 1804)

• Definition: Default classes for linear and angular dimensions not individually toleranced (f/m/c/v).

• Usage recommendation: State on the drawing “General tolerances per ISO 2768-m (or GB/T 1804-m).” 

• Purchasing/quality tips: Misaligned default class vs. supplier’s preset can cause rework; align before RFQ.

• GD&T systems (ISO 1101 vs ASME Y14.5)

• Definition: Both systems control form, orientation, location, and runout via symbolic language; syntax details differ (e.g., composite controls, datum establishment).

• Design/manufacturing tips: Avoid “mixing” symbols; for 3D/MBD projects, specify which system is used.

• Purchasing/quality tips: Gaging and measurement programs must match the chosen system; align measurement report templates accordingly.

Surface Roughness

• Ra / Rz (ISO 21920 series)

• Definition: Ra is arithmetic mean roughness; Rz is the average peak-to-valley height over multiple sampling lengths (more sensitive to extremes).

• Common ranges: For milled/turned parts, Ra ≈ 0.8–3.2 μm is common; precision machining/grinding can go lower; values vary with tooling, feed/path, and material.

• Standards update: ISO 21920-1/-2/-3:2021 supersedes legacy ISO 1302/4287/4288/13565, unifying parameters and indication rules. 

• Design/manufacturing tips: Indicate evaluation length, filtering, and sampling locations to avoid acceptance disputes; for legacy drawings, add “equivalent parameter” migration notes where needed.

• Purchasing/quality tips: Roughness targets affect toolpath, pricing, and lead time; confirm during RFQ.

Inspection and Environmental Testing

• CMM (Coordinate Measuring Machine)

• Definition: High-precision measurement of dimensions and GD&T; performance is commonly given as MPE (e.g., MPE_E = a + L/b μm).

• Design/manufacturing tips: In GD&T projects, align default assumptions on fixturing, probe compensation, and datum selection.

• Purchasing/quality tips: Require supplier calibration certificates and measurement procedures; provide fixtures or measurement sketches for complex features.

• Salt spray test (ISO 9227 / ASTM B117)

• Definition: Evaluates corrosion resistance in an artificial salt fog; common modes are NSS (neutral), AASS, CASS.

• Standards reference: ISO 9227:2022 defines apparatus and procedures; ASTM B117-19 is a widely used practice. Intended for comparative screening rather than direct real-life lifetime conversion. See the EN ISO 9227:2022 catalog page (CEN).

• Design/manufacturing tips: Define test type, hours, and criteria (blistering, corrosion spot counts, etc.).

• Purchasing/quality tips: Roles differ between outgoing inspection and type test; use third-party lab witnessing when necessary.

Quality Systems and Compliance

• ISO 9001 (current 2015 edition)

• Applicable to: General quality management; focuses on process control and continuous improvement.

• IATF 16949 (2016, automotive)

• Applicable to: Automotive quality management; often layered with customer-specific requirements (CSR).

• AS9100D (aerospace)

• Applicable to: Aerospace quality systems; emphasizes configuration management and special process control.

• Purchasing/quality tips: Certification does not equal zero defects; execution still relies on drawings, process cards, and measurement/inspection plans.

Purchasing Parameters and Implementation Tips

• Material and traceability: Alloy and temper, heat/lot number, MTC (Mill Test Certificate). Consistency risks arise across lots and when substitutes are used.

• Process and lead time: Machine scheduling plus outsourced surface finishing stack up; dyed anodizing often has a minimum order quantity (MOQ).

• Consistency and appearance: Same lot/line/process window helps reduce shade variation; for appearance parts, communicate with sample cards and color IDs.

• Inspection and acceptance: Align gage list, sampling plan, and measurement methods for thickness/roughness/dimensions before contract signature.

Alloys & Tempers

Aluminum alloy names and tempers follow the Aluminum Association’s designation system used in the American National Standard. See the association’s overview of the framework in the Aluminum Association — ANSI H35.1/H35.1M page and the registered composition listings in the AA Teal Sheet (wrought, 2021) and AA Purple Sheets (cast, 2022).

• 1xxx–7xxx (wrought series)

• Definition: Four-digit series describing major alloying elements (e.g., 5xxx = Mg, 6xxx = Mg+Si, 7xxx = Zn+Mg). Composition registrations appear in AA Teal Sheets.

• Design/manufacturing tips: 6xxx is widely extrudable and weldable (e.g., 6061, 6063). 5xxx offers good corrosion resistance and formability (e.g., 5052). 7xxx enables high strength (e.g., 7075) but may reduce weldability and SCC resistance in certain tempers.

• Procurement/QA notes: Specify alloy + temper (e.g., 6061-T6). Verify chemistry and mechanicals via MTC linked to heat/lot.

• Temper designations (F, O, H, W, T + digits like T6/T651/H32)

• Definition: Heat treatment/strain-hardening conditions per ANSI H35.1/H35.1M (formal text in standard). Example: T6 = solution heat-treated and artificially aged; T651 = T6 plus stress-relieved by stretching; H32 = strain-hardened and stabilized.

• Tips: Temper affects strength, machinability, formability, and residual stress. Stress-relieved tempers (e.g., T651) help dimensional stability in machining.

• QA: Confirm temper on MTC; for critical parts, consider hardness and conductivity checks as proxies for heat treat condition.

• 6061 (common 6xxx)

• Definition: Mg+Si wrought alloy used in extrusions and plate; balanced strength/weldability.

• Tips: 6061-T6 machines well; 6061-T651 plate resists warping. Consider anodic color variability across lots.

• QA: Typical 6061-T6 tensile properties are referenced in ASM/MatWeb-style datasheets; treat values as typical, verify per MTC. See, for example, the ASM/MatWeb 5052-H32 page as a typical data reference format (use the appropriate sheet for 6061 when sourcing data).

• 6063 (extrusion-friendly)

• Definition: Highly extrudable 6xxx alloy for architectural profiles; excellent surface finish.

• Tips: Often chosen for thin, complex profiles where surface appearance matters.

• QA: Confirm profile temper (e.g., T5 vs T6) due to strength differences.

• 5052 (formable 5xxx)

• Definition: Mg alloy known for good corrosion resistance and moderate strength; often in sheet.

• Tips: Preferred for bending/forming and marine applications; not heat-treatable.

• QA: H32/H34 tempers common; verify bend radii capability by temper and thickness.

• 7075 (high-strength 7xxx)

• Definition: Zn+Mg alloy with very high strength; aerospace uses common.

• Tips: T6 is strong but more SCC-susceptible; over-aged tempers (e.g., T73) improve SCC resistance at some strength cost.

• QA: Check heat treatment and mechanicals carefully; anodizing color may vary vs 6xxx due to metallurgy.

See also: Design overviews and alloy trade-offs in Metal Materials.

Processes

• Extrusion

• Definition: Forcing heated billet through a die to create continuous profiles.

• Tips: Wall-thickness ratios and die land lengths limit feature geometry; consider corner radii and uniform wall to reduce distortion.

• QA: Expect die lines and slight twist/bow; define straightness and twist limits on profile drawings.

• Rolling (sheet/plate)

• Definition: Reducing thickness by rolling; may be followed by heat treatment and leveling.

• Tips: Grain direction anisotropy affects bending; align bends with favorable grain orientation.

• QA: Specify flatness and thickness tolerances by product standard when critical.

• Forging

• Definition: Plastic deformation in dies to refine grain and increase strength.

• Tips: Good for high-load components; machining stock and draft angles required.

• QA: Confirm forging stock alloy/temper and NDT requirements where applicable.

• Casting (sand, permanent mold, die)

• Definition: Forming parts from molten aluminum into molds of varying permanence/pressure.

• Tips: Die casting yields fine details but may entrap gas; heat treatment options depend on alloy.

• QA: Define porosity acceptance, leak tests, and machining stock.

• CNC machining (milling/turning)

• Definition: Subtractive shaping via machine tools.

• Tips: Use stable tempers (e.g., T651 plate). Tool selection and coolant affect burrs and finish. For DFM practices see CNC Machining.

• QA: Agree on inspection datum scheme and sampling; confirm machine capability for required tolerances.

• Welding and brazing

• Definition: Joining metals by fusion (welding) or filler melting below base metal (brazing).

• Tips: 6xxx weldable with proper filler; 7xxx often challenging. Post-weld heat treatment may be necessary for strength recovery.

• QA: Specify weld process (e.g., GTAW), NDT (dye penetrant), and acceptance per code.

• Heat treatment (solution, aging, stress relief)

• Definition: Thermal cycles to set temper and properties.

• Tips: Distortion risk on thin parts; fixturing and stress-relief stretching reduce warp.

• QA: Reference temper callouts; request furnace charts when critical.

Surface Treatments

• Anodizing — types/classes and drawing callouts

• Definition: Electrochemical oxidation forming an aluminum oxide layer for corrosion/wear resistance or aesthetics. U.S. defense work commonly references MIL-PRF-8625, which defines anodic coating types/classes and key process controls; see the industry summary by the Aluminum Anodizers Council on MIL anodize.

• Tips: On drawings/RFQs, specify spec + Type (II or III typical), Class (1 = non-dyed; 2 = dyed), thickness (µm or mil), color (if dyed), sealing requirement, and any critical measurement/acceptance locations.

• QA: For disputes on thickness, eddy-current is common NDT but is substrate/geometry sensitive; consider agreeing arbitration by microsection in technical terms.

• Anodic coating thickness measurement

• Definition: Eddy-current NDT is standardized in ISO 2360 (catalog abstract) and, for anodize, in ASTM B244-09(2021). Cross-section microscopy provides referee results per ISO 1463/ASTM B487.

• Tips: Calibrate on like alloy/temper/surface; avoid edges and small radii; document probe frequency and reference foils.

• QA: Define acceptance locations and sampling size; for hardcoat, consider microsection arbitration for disputed readings.

• Conversion coating (chromate; TCP)

• Definition: Chemical conversion films for paint adhesion and corrosion resistance. MIL-DTL-5541 defines Class and Type; Type II indicates hexavalent-chrome-free chemistries (e.g., TCP). Use DoD ASSIST for current specs.

• Tips: Specify Class (e.g., Class 1A for maximum protection or Class 3 for conductivity) and electrical continuity needs.

• QA: Require bath control records when critical; confirm RoHS/REACH compliance for hexavalent-chrome-free builds.

• Powder coat / Liquid paint

• Definition: Organic coatings for protection/color; require suitable pretreatment (e.g., conversion coat).

• Tips: Specify color standard (e.g., RAL), film thickness, gloss, cure schedule, and adhesion test.

• QA: Agree on defect acceptance (orange peel, runs, inclusions) and repair limits.

Metrology & GD&T

• Surface texture (roughness) — ISO 21920

• Definition: The ISO 21920 series updates profile specification/measurement, replacing legacy ISO 4287/4288/1302. Part 1 covers drawing indication rules;

• Tips: Indicate parameters (Ra, Rz, etc.) with filters, evaluation length, and section length per ISO 21920-1. Avoid Ra-only for functional sealing/wear surfaces; consider Rz/Rmr.

• QA: Ensure instrument settings match the specified filters/lengths; mismatches cause disputes.

• General tolerances — ISO 2768-1

• Definition: Provides default linear/angular tolerances when not individually specified; declare grade (f, m, c, v) on the drawing. 

• Tips: Put “ISO 2768-m” (or chosen grade) in the title block; do not mix with ASME default blocks.

• QA: Align supplier capability with the chosen grade; confirm flatness/straightness expectations separately if critical.

• GD&T frameworks — ISO 1101 vs ASME Y14.5

• Definition: ISO 1101 is part of the ISO GPS system; ASME Y14.5 is the North American standard for geometrical dimensioning and tolerancing. See ISO 1101 OBP abstract and ASME Y14.5 overview.

• Tips: Choose one system per project and state it clearly to avoid interpretation conflicts.

• QA: Ensure CMM programs, datum precedence, and tolerances are implemented in the same system selected on the drawing.

• CMM capability and MPE (ISO 10360-2)

• Definition: ISO 10360-2 governs acceptance/reverification tests for CMM length measurement error. Manufacturers specify MPEE (length), MPEP (probing), etc.; see the ISO 10360-2 catalog abstract.

• Tips: Request current calibration certificates and the CMM’s specified MPE relative to your tolerance stack.

• QA: Align measurement strategy (probing force, stylus, scanning vs touch) with feature geometry and tolerance type.

Corrosion & Behavior

• Pitting corrosion

• Definition: Localized attack forming pits, often accelerated by chlorides.

• Tips: Avoid crevices and stagnant saltwater; consider 5xxx/6xxx with protective finishes for marine environments.

• QA: Do not use salt spray hours as a direct life predictor; treat as comparative screening only (see standards in Section G/H).

• Galvanic corrosion

• Definition: Corrosion of the less noble metal when dissimilar metals are electrically connected in an electrolyte.

• Tips: Electrically isolate aluminum from stainless/steel in wet environments; use compatible fasteners or insulating washers.

• QA: Specify conversion coating/anodize and sealant where dissimilar contacts are unavoidable.

• Stress corrosion cracking (SCC)

• Definition: Crack growth under tensile stress and corrosive environment; certain 7xxx tempers are more susceptible than 6xxx. Aerospace practice often uses over-aged tempers (e.g., T73) for SCC mitigation.

• Tips: Minimize sustained tensile stress; consider T73/T74 for 7xxx when environment or safety factors dictate.

• QA: For critical parts, reference applicable material and process specs (AMS/MMPDS) and environmental tests.

Standards & Specifications (application-first map)

• Alloy designation and registration

• Use the Aluminum Association framework per ANSI H35.1/H35.1M with compositions in AA Teal Sheet and AA Purple Sheets.

• Anodizing

• For non-architectural applications, MIL-PRF-8625 defines types/classes and controls; see the AAC overview of MIL anodize. Specify Type, Class, thickness, sealing, color, and measurement method.

• Coating thickness measurement

• Reference ISO 2360 for eddy-current and ASTM B244 for anodic coatings; specify arbitration method (ISO 1463/ASTM B487) where needed.

• Surface texture

• Specify roughness per ISO 21920-1 with filters and lengths on drawings.

• General tolerances and GD&T

• For default dimension tolerances use ISO 2768-1. Choose either ISO 1101 (GPS) or ASME Y14.5 for geometrical tolerancing and declare it.

• Salt spray

• ISO 9227 and ASTM B117 govern apparatus/procedure; they are screening methods and not predictive of service life. 

Procurement & QA

• Mill Test Certificate (MTC/MTR) and EN 10204

• Definition: Documented chemical/mechanical properties tied to heat/lot, commonly structured per EN 10204 (types 2.1, 2.2, 3.1, 3.2). 

• Tips: Require EN 10204 type (often 3.1) in RFQs/POs and trace lot IDs through finishing.

• QA: For regulated sectors, align supplier quality system (e.g., IATF/AS9100) and retain MTCs and process certs in the Device History Record (DHR) or traveler.

• Sampling & acceptance

• Definition: Agreement on AQL, critical-to-quality features, and inspection level.

• Tips: List measurement equipment and reference standards; define arbitration methods (e.g., microsection for anodize thickness).

• QA: Ensure CMM capability vs tolerance; request ISO 10360-2 evidence for length/probing performance.

• Supplier capability & gaging

• Definition: Demonstrated ability to meet tolerances with calibrated gages and programs.

• Tips: Share datum schemes and GD&T early; dry runs prevent misinterpretation.

• QA: Keep calibration certificates current and traceable to national standards.

Defects & Troubleshooting

• Extrusion: die lines, tearing, bow/twist, wavy walls

• Causes: Die wear, uneven flow, cooling/handling stresses.

• Mitigation: Die maintenance, balanced wall thickness, controlled quench/stretch; define straightness and twist limits.

• Anodizing: color variance (“yin–yang”), burning, chalking

• Causes: Alloy/temper differences, bath conditions, current density, sealing quality.

• Mitigation: Pre-approved color chips, batch control, alloy grouping; specify sealing and measurement method.

• Powder/paint: orange peel, runs, inclusions, fisheyes

• Causes: Film thickness variance, contamination, improper cure.

• Mitigation: Cleanliness, controlled cure schedule, film gauges; define rework rules.

• Machining: chatter, burrs, dimensional drift

• Causes: Tool wear, workholding rigidity, residual stress release.

• Mitigation: Sharp tools, stable tempers (e.g., T651), strategic roughing/finishing passes; verify fixturing and thermal stability.

• Welding: porosity, lack of fusion, undercut

• Causes: Contamination, gas flow issues, improper heat input.

• Mitigation: Proper cleaning, parameter control, qualified procedures; NDT per code.

Regulatory & Compliance

• RoHS (EU 2011/65/EU)

• Definition: Restricts hazardous substances in EEE; limits hexavalent chromium to 0.1% w/w in homogeneous materials. See the consolidated law text at EUR-Lex — Directive 2011/65/EU.

• Tips: Specify hexavalent-chrome-free conversion coatings (Type II per MIL-DTL-5541) where applicable.

• REACH SVHC

• Definition: Candidate List substances trigger communication/notification above 0.1% w/w in articles; hexavalent chromium compounds are included. See ECHA — Candidate List table.

• Tips: Collect supplier declarations and, when necessary, laboratory screening.

• Trivalent Chromium Process (TCP)

• Definition: Hexavalent-chrome-free conversion coating chemistry used to meet MIL-DTL-5541 Type II; qualifying materials are covered by MIL-DTL-81706 (consult DoD ASSIST for current details).

• Tips: Confirm electrical conductivity requirements vs Class selection (e.g., Class 3).

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