ISO 24021-1:2022

Light gauge metal containers - Vocabulary and classification - Part 1: Open-top cans and ends

This document defines terms and establishes a classification (see Annex A) for open-top metal cans and metal ends. This document is applicable to open-top metal cans and metal ends for food and beverages made of metal plates such as tin or chromium-coated steel plates or aluminium alloy plates with a thickness of no more than 0,49 mm.

Récipients métalliques légers — Vocabulaire et classification — Partie 1: Boîtes serties à extrémité sertie

General Information

• Status: Published
• Publication Date: 25-Aug-2022
• ICS: 01.040.55 - Packaging and distribution of goods (Vocabularies)
• ICS: 55.120 - Cans. Tins. Tubes
• Technical Committee: ISO/TC 52 - Light gauge metal containers
• Drafting Committee: ISO/TC 52/WG 2 - Terminology and classification
• Current Stage: 6060 - International Standard published
• Start Date: 26-Aug-2022
• Due Date: 08-May-2023
• Completion Date: 26-Aug-2022

Overview

ISO 24021-1:2022 - Light gauge metal containers - Vocabulary and classification - Part 1: Open-top cans and ends, is an ISO international standard that defines terminology and establishes a classification for open-top metal cans and metal ends used for food and beverages. It applies to containers made from tinplate, electrolytic chromium/chromium‑oxide coated steel or aluminium‑alloy plates with a maximum thickness of 0.49 mm. The standard provides a unified vocabulary and a classification scheme (see Annex A) to improve clarity and reduce trade barriers in the light gauge metal container sector.

Key topics and technical content

This document focuses on standardized definitions and classification rather than prescriptive performance tests. Major technical topics covered include:

• Raw and processed materials: terms for tinplate, electrolytic tinplate, coated tinplate, aluminium alloy and laminated materials.
• Manufacturing techniques: definitions for can body, flanging, drawing, necking, roll‑forming, embossing, seaming (double seam), seaming roll/chuck/rail, sealing and easy‑open features (tab, score, rivet).
• Seam and closure terminology: seam height/width/thickness, body hook, cover hook, countersink depth, length/rate of overlap, seam gap.
• Quality and defects vocabulary: wrinkle rating (WR), tightness rating (TR), juncture/cover/body hook butting, false seam, jumped seam, welding defects (pin hole, puncture), score defects and other seam faults.
• Evaluation terms: enamel rate value (ERV), splash, compound and sealing gasket definitions.
• Classification: informative Annex A provides a classification framework for open‑top cans and ends to support consistent identification and communication.

Practical applications

ISO 24021-1:2022 is intended to be used where consistent terminology and classification are essential:

• Specifying product requirements in procurement documents and technical specifications for food and beverage packaging.
• Creating clear design and manufacturing documentation for can manufacturers, converters and metal‑packaging suppliers.
• Supporting quality assurance, inspection and laboratory reporting by providing agreed definitions of defects, seams and ratings.
• Aiding machine manufacturers (seamers, sealers) and tooling suppliers to align terminology with customers.
• Facilitating international trade, regulatory communication and standardization work by preventing ambiguity in product descriptions.

Who should use this standard

• Can and end manufacturers, packaging engineers, QA/QC inspectors, procurement specialists, regulatory bodies, testing laboratories and standards committees.

Related standards

• Other parts of the ISO 24021 series and documents produced by ISO/TC 52 (Light gauge metal containers) covering additional container types and complementary terminology.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 24021-1
First edition
2022-08
Light gauge metal containers —
Vocabulary and classification —
Part 1:
Open-top cans and ends
Récipients métalliques légers — Vocabulaire et classification —
Partie 1: Boîtes serties à extrémité sertie
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Terms related to raw and processed materials . 1
3.2 Terms related to manufacturing technique . 3
3.3 Terms related to quality . 5
3.4 Terms related to evaluating the quality and safety of containers containing food .12
3.5 Terms related to classification . 16
Annex A (informative) Classification .29
Bibliography .31
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 52, Light gauge metal containers.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The definitions in this document have been drawn up with the objective of achieving a proper balance
between precision and simplicity. This document has been developed to provide a unified standard
set of terms and definitions of open-top cans and ends. Some terminology of open-top cans and ends in
present use has developed through common usage and is not always logical. It has not, therefore, been
possible to define certain terms in the form they are used in some countries. Because of the occasional
conflicts between tradition and logic, some definitions inevitably represent a compromise.
The classification is a common technique that humans use to cope with the complexity of the world
around us. Since there are many different possible application areas, there is no single classification
system that will serve all needs. The method by which classifiers are defined depends upon the
application area. In addition, the classifiers used within a particular application area might not be
adequate for all situations.
This document has been developed to help prevent trade barriers and enhance communication.
v
INTERNATIONAL STANDARD ISO 24021-1:2022(E)
Light gauge metal containers — Vocabulary and
classification —
Part 1:
Open-top cans and ends
1 Scope
This document defines terms and establishes a classification (see Annex A) for open-top metal cans and
metal ends.
This document is applicable to open-top metal cans and metal ends for food and beverages made of
metal plates such as tin or chromium-coated steel plates or aluminium alloy plates with a thickness of
no more than 0,49 mm.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Terms related to raw and processed materials
3.1.1
tinplate
non-alloy, low carbon steel supplied in strip or sheet form that has been single or double cold reduced
and coated on both surfaces with tin in a continuous electrolytic process
Note 1 to entry: Single-reduced tinplate is commonly supplied with a thickness of 0,15 mm up to and including
0,60 mm, double-reduced tinplate with a thickness of 0,14 mm up to and including 0,36 mm. Tinplate is supplied
normally with a passivation treatment and a protective coating of oil and is suitable for varnishing (lacquering)
or printing.
Note 2 to entry: Tinplate may also be obtained by hot dipping in a bath of molten tin.
[SOURCE: ISO 6929:2013, 1.3.4.2]
3.1.2
electrolytic tinplate
cold-reduced low-carbon steel sheet or coil coated on both surfaces with tin that is applied in a
continuous electrolytic operation
[SOURCE: ISO 11949:2016, 3.2]
3.1.3
electrolytic chromium/chromium oxide-coated steel
cold-reduced low-carbon mild steel sheet or coil, electrolytically treated to produce on both surfaces a
duplex film of metallic chromium adjacent to the steel substrate with a top layer of hydrated chromium
oxide or hydroxide
[SOURCE: ISO 11950:2016, 3.2]
3.1.4
single cold-reduced
description of product in which the blackplate has been reduced to the desired thickness in a cold-
reduction mill and subsequently annealed and temper rolled
[SOURCE: ISO 11949:2016, 3.4]
3.1.5
double cold-reduced
description of product in which the blackplate has had a second major reduction after annealing
[SOURCE: ISO 11949:2016, 3.5]
3.1.6
K plate
electrolytic tinplate, No. 50 or heavier tin coating, with good corrosion resistance
Note 1 to entry: The target value should meet the following requirements after four special tests, the pickling lag
(PL), iron solution value (ISV), tin crystal size (TCS) and alloy-tin electrical coupling (ATC):
a) PLV ≤ 10 s;
b) TCS ≤ 9 grade;
c) ISV ≤ 20 μg;
d) ATC ≤ 0,12 μA/cm .
3.1.7
J plate
electrolytic tinplate, No. 50 or heavier tin coating, with good corrosion resistance
Note 1 to entry: The target value should meet the following requirements after three special tests, the pickling
lag (PLV), iron solution value (ISV) and tin crystal size (TCS):
a) PL ≤ 10 s;
b) TCS ≤ 9 grade;
c) ISV ≤ 20 μg.
3.1.8
aluminium alloy
alloy with a mass fraction of aluminium greater than 50 %
3.1.9
coated tinplate
tinplate (3.1.1) strip or sheet coated with lacquer and cured at high temperature to form a film
3.1.10
coated tin free steel
electrolytic chromium (3.1.3) strip or sheet coated with lacquer and cured at high temperature to form
a film
3.1.11
coated aluminium alloy
aluminium alloy (3.1.8) strip or sheet coated with lacquer and cured at high temperature to form a film
3.1.12
aluminium foil
very thin aluminium coil, strip or sheet made of aluminium and aluminium alloy (3.1.8) plate and strip
after rolling
3.1.13
laminated steel
composite material with dual properties of organic polymer material and metal material formed by
gluing a layer of polymer film on the surface of a tinplate (3.1.1) or chrome-plated steel sheet through
the melting method
3.1.14
laminated aluminium
composite material with dual properties of organic polymer material and metal material formed by
gluing a layer of polymer film on the surface of the aluminium alloy (3.1.8) sheet by melting
3.1.15
compound
sealing material formulated with latex or rubber, filler and tackifier
Note 1 to entry: The material is poured into the round ditch of the can lid in a slope shape inclined to the centre of
the can lid. After forming a double crimp, it is filled in the gap at the bottom of the lid groove and squeezed on the
first and second layers of the outer side of the crimp. The gap between the metal plates serves as a seal.
3.1.16
sealing gasket
plastic or rubber ring/pad with a certain thickness attached to the inner surface of the metal cap
3.2 Terms related to manufacturing technique
3.2.1
can body
principal part of the container (usually the side wall formed by the largest part of a single piece), which
has a round, square or other shape
3.2.2
resistance welding
welding with pressure in which the heat necessary for welding is produced by resistance to an electrical
current flowing through the welding zone
[SOURCE: ISO/TR 25901-3:2016, 2.2.1.7.1]
3.2.3
flanging
upper edge of the can that is flared out at right angles to the vertical axis of the can
3.2.4
roll-forming
cylinder formed by the can body plate after the rounding device, which has a gap of 4 mm to 6 mm on
the side of the cylinder and is parallel along the length of the cylinder
3.2.5
necking
punching method for reducing the diameter of the open top of a cylindrical blank
3.2.6
embossing
printing process that uses a concave and convexity mould to form printed material deformation under a
certain pressure to form a pattern on the surface
3.2.7
drawing
processing method that uses the extensibility of metal materials by drawing die to put a blank or semi-
finished product of a certain shape into a mould to form an open hollow can
3.2.8
ink-jet printing
process of marking product information on can ends or labels with a printer
3.2.9
sealing of metal can
process in which semi-finished products are put into metal cans and sealed with a can-sealing machine
3.2.10
seaming roll
main part on a can seamer with two small round wheels with different curvatures around that forms
the double-seam structure, in which the first roller is to roll the can cover hook (3.2.19) under the can
body flange and roll them together, and the second roller is to press the first roller tightly, so that the
curling is tightly combined with each other, and the sealant is filled inside the forming gap between the
can body and the cover hook (3.2.19)
3.2.11
seaming rail
sealing accessory part of the high-speed sealing machine, which replaces the roller, forms a double
seam and meets the sealing requirements
3.2.12
seaming chuck
part of the can sealing machine that can be embedded in the countersunk part of the can cover and
support the combined part of the can cover and the can body with the peripheral side to resist the
pressure of the sealing roller
3.2.13
base plate
part that lifts the can lid and the can body upward when the can sealing machine is running, so that
the pressure head is embedded in the can lids, and the can body is stabilized to avoid sliding, so as to
facilitate the formation of double curling and meet the sealing requirements
3.2.14
double seam
sealing structure formed by the operation of the first roller and the second roller to make the flanging
of the can body and the hook of the cover (bottom) overlap each other and press tightly, which is
composed of three layers of top (bottom) cover thickness and two layers of can body thickness
3.2.15
seam thickness
maximum external dimension measured across or perpendicular to the body and cover hook
3.2.16
seam height
seam length
seam width
maximum external dimension of a seam measured parallel to the body and end hook
3.2.17
countersink depth
distance from the top radius of the double seam to the bottom of the countersink radius
3.2.18
body hook
folding over of the body flange into an interlocking hook
3.2.19
cover hook
hook formed from the cover curl extending from the radius to an opposite (180°) radius
3.2.20
tab
ring-shaped or other shaped structure which is staked with the ends for easy opening
3.2.21
score
tear line pre-pressed or scored on the easy-open ends (3.5.22) for easy opening
3.2.22
rivet
fixed part of the easy-open ends (3.5.22) to rivet the retaining piece (pull ring)
3.2.23
curl
extreme edge of the can end which is turned inward when the double seam is formed to become the end
hook
3.2.24
score repairing
repairing process at the score area of the end where the coating is destroyed during the formation of
the score
3.3 Terms related to quality
3.3.1
length of overlap
actual overlap
measurement of how much the body hook (3.2.18) overlaps the cover hook (3.2.19)
3.3.2
seam gap
place between the top of the body hook radius and the underside of the seaming panel
3.3.3
rate of overlap
percentage of overlap
ratio of the length of overlap (3.3.1) relative to the internal seam length, expressed as a percentage
3.3.4
wrinkle rating
WR
degree of waviness occurring in the cover hook (3.2.19) from which the degree of double seam tightness
is determined
Note 1 to entry: Wrinkles are not included in the sealing process. The marks left after the wrinkles are rolled and
smoothed.
Note 2 to entry: See Figure 1.
a
Wrinkles.
b
Tightness.
Figure 1 — Wrinkles and tightness
3.3.5
tightness rating
TR
measure of the degree of wrinkle left on the end hook on the completed double seam
Note 1 to entry: See Figure 1.
3.3.6
juncture rating
JR
percentage of the cover hook (3.2.19) metal available for overlap when it is interlocked with a body hook
(3.2.18)
3.3.7
cover hook butting
CHB
percentage of the can cover hook (3.2.19) at the overlap of the seam to the theoretical cover hook (3.2.19)
length
3.3.8
body hook butting
BHB
percentage of the can body hook (3.2.18) at the overlap of the seam to the theoretical body hook (3.2.18)
length
3.3.9
ridge
continuous impression around the inside periphery of the can body in the double seam area formed by
the seaming roll pressure
3.3.10
enamel rate value
ERV
evaluation of the undesired metal exposure by checking the integrity of the coating using current value
3.3.11
splash
spikes of metal extending from the weld due to excessive heating at the site of the spatter
3.3.12
false welding
pseudo welding
cold weld
welding when two plates to be welded have not reached the plastic-welded state (only the tin is melted)
due to a low welding temperature
3.3.13
welding pin hole
cavities that can appear in a melded puddle after two pieces of metal are welded together
3.3.14
welding puncture
individual welding spots melt and perforated due to sudden excessive welding current
3.3.15
missing welding
one or more welding points fail to weld due to no current or too small current
3.3.16
faulty score
excessively deep or weak scoreline during the scoring process
3.3.17
dead head
spinner
skidder
slip seam
incompletely ironed out double seam
Note 1 to entry: See Figure 2.
Key
1 normal seam
2 skidder
Figure 2 — Dead head; spinner; skidder; slip seam
3.3.18
off-set
defect where the weld port is not flat due to a poor end lap
3.3.19
fishtail
defect where the end of the weld is protruding due to poor welding
3.3.20
jumped seam
defect where the hemming at the weld is thicker and the roller skips when passing through the weld
and fails to compress the hemming
Note 1 to entry: See Figure 3.
Key
1 jumped seam
2 juncture seam
Figure 3 — Jumped seam
3.3.21
false seam
false seal
seam or portion of a seam that is entirely unhooked and in which the folded cover hook (3.2.
...