Aluminium extrusion defects

A classification of surface defects in aluminium profiles

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Get insights into a classification of surface defects in aluminium profiles. Learn about blisters, cracking, tearing, and other common issues.

This classification of surface defects in extruded aluminium profiles from common 6ххх alloys based on two authoritative sources:

  1. Extrusion Defects Fundamentals & Solutions for Optimum Finish / Jerome Fourmann (Rio Tinto), May 2017.
  2. The Identification and Prevention of Defects on Anodized Aluminum Parts / Ted Short, Metal Finishing Information Service, 2003   

Common 6xxx series aluminum alloys

“Soft” 6xxx aluminium alloys

  • 6360 “Improving the properties”
  • 6063 “General purpose”
  • 6063 “Increased strength” -T54, -T65

Medium-strength 6xxx aluminium alloys

  • 6005A
  • 6061/6351 (6061 – analog AD33)
  • 6082 (AD35 analog)

A classification of surface defects in aluminium profiles

Extrusion defects

  • Pick-ups
  • Blisters
  • Speed cracking
  • Tearing
  • Die lines
  • Micro die lines
  • Die streaks
  • Snap mark
  • Front-end transverse weld
  • Back-end coring
  • Longitudinal weld
  • Hot spots

 Metallurgical and processing  defects

  • Coarse Mg2Si
  • Mg2Si at grain boundary
  • Coarse grain banding
  • Orange peel
  • Corrosion pitting
  • Corrosion fingerprint
  • Corrosion fretting
  • Water stain
  • Spacer marking
  • Excess lubricant
  • Cast inclusions

Anodising defects

  • Atmosphere corrosion
  • Acid corrosion
  • Alkali corrosion
  • Rinse water corrosion
  • Chloride contamination
  • Dull finish
  • Coloring due to Mg2Si
  • White etch bloom
  • Spangle
  • Inadequate rinsing
  • Castle and moat
  • Anodizing burn
  • Loss of electrical contact

Sources:

  1. Extrusion Defects Fundamentals & Solutions for Optimum Finish / Jerome Fourmann (Rio Tinto), May 2017.
  2. The Identification and Prevention of Defects on Anodized Aluminum Parts / Ted Short, Metal Finishing Information Service, 2003