ISO 17212:2012

INTERNATIONAL ISO
STANDARD 17212
Second edition
2012-02-15
Structural adhesives — Guidelines for
the surface preparation of metals and
plastics prior to adhesive bonding
Adhésifs structuraux — Lignes directrices pour la préparation de
surface de métaux et de plastiques avant le collage par adhésif
Reference number
©
ISO 2012
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Published in Switzerland
ii © ISO 2012 – All rights reserved

Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
1.1 General . 1
1.2 Surfaces . 1
1.3 Methods . 2
2 Normative references . 3
3 Terms and definitions . 3
4 Safety . 3
5 Initial preparative techniques . 4
5.1 General . 4
5.2 Handling, cleaning and storing. 4
6 Surface modification . 5
6.1 Physical: Mechanical (scarification) . 5
6.2 Physical: Non-mechanical . 6
6.3 Chemical . 6
6.4 Combined procedures . 9
7 Preparative procedures .10
7.1 General .10
7.2 Specific . 11
8 Evaluation of durability .26
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 17212 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 11, Products.
This second edition cancels and replaces the first edition (ISO 17212:2004), which has been technically revised.
iv © ISO 2012 – All rights reserved

Introduction
Some materials will bond far better than others and some will not bond at all without special treatment. The
suitability of a surface for bonding depends upon the degree of surface preparation, the joint’s design, the
function it has to perform (joining, sealing, etc.) and the environment it has to perform in.
Prior to bonding, some degree of surface preparation is required for most adhesives — but not all. Material
surfaces that are particularly prone to weak or loose surface layers, stress cracking or solvent attack usually
require special treatment.
Following appropriate preparation, most common metals and their alloys can be bonded satisfactorily. Were
it not for contamination and residual mould release agents, thermoset plastics (e.g. polyepoxy and polyester
composites) would bond well without any preparation. By contrast, most thermoplastics require careful
preparation because of their low surface energy.
Some paints — especially the cataphoretic, water-based primers used by the vehicle industries — can provide an
excellent surface for bonding. However, the stability of the interface below the paint should be checked. The surface
of the paint itself, even if fresh, can require treatment in order to raise its free energy and thus facilitate wetting.
Certain adhesives possess the ability to dissolve light oils and some polymeric materials. Consequently, for
joints that are not “safety-critical” some surfaces do not require any preparation prior to bonding.
In order to achieve the optimum environmental durability from a bonded joint, the traditional preparative
approach usually, though not necessarily, consisted of three sequential steps:
— the removal of contaminants;
— physically induced modification of the surface to be bonded;
— chemical treatment.
However, legislative pressure is driving development and the introduction of new methods. Consequently, the
separate steps of the foregoing sequence are being combined and the more hazardous chemicals are being
progressively eliminated.
The majority of both thermoset and thermoplastics materials can be prepared by commonly applicable
techniques — though there will often be detailed differences. By contrast, metal and metal-alloy surfaces to be
bonded generally require individual treatment. The optimization of the durability of a metal-based joint usually
requires the introduction of progressively more complex and specific treatments.
Such process options are described for a number of metals and their alloys, and some plastics (see Clause 7).
INTERNATIONAL STANDARD ISO 17212:2012(E)
Structural adhesives — Guidelines for the surface preparation
of metals and plastics prior to adhesive bonding
1 Scope
1.1 General
This International Standard provides and describes the usual procedures for the preparation of component
surfaces prior to bonding for either laboratory evaluation or the process of construction. This International
Standard is applicable to metal and plastic surfaces that are commonly encountered.
1.2 Surfaces
These comprise the following metal, metal-alloy and plastic families — the last-mentioned including filled
versions and suitable paints:
Metals and metal alloys
aluminium
chromium
copper
magnesium
nickel
steel (mild)
steel (stainless)
tin
titanium
zinc
Paints
cataphoretic (water-based)
poly-alkyd
ester
epoxide
urethane
Plastics
Thermoplastic
acrylonitrile-butadiene-styrene copolymer
poly-acetal
acrylate
amide
butylene terephthalate
carbonate
ester
ether ether ketone
ethylene
imide
methyl methacrylate
phenylene oxide
propylene
styrene
sulfone
tetrafluoroethylene
vinyl chloride
Thermoset
cellulose-based esters
poly-alkyd
allyl phthalate
amino
epoxide
ester
phenolic
urethane
urea-based (see poly-amino above)
1.3 Methods
The various techniques described for cleaning and modifying surfaces are drawn from the best of current
practice. The methods can be used in a variety of combinations to create the most effective preparative process
conducive with the environmental durability required of the bonded joint.
2 © ISO 2012 – All rights reserved

2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 472, Plastics — Vocabulary
EN 923, Adhesives — Terms and definitions
EN 2243-5, Aerospace series — Non-metallic materials — Structural adhesives — Test methods —
Part 5: Ageing tests
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 472 and EN 923, together with the
following, apply.
3.1
plastic
material which contains, as an essential ingredient, a high polymer and which, at some stage in its processing
into finished products, can be shaped by flow
NOTE 1 For the specific requirements of this International Standard, “plastic” also includes paint. In this latter context,
it needs be realized that only a few paint surfaces are capable of supporting anything other than purely nominal loads.
The exceptions are typically those based upon aqueous, electrochemical paints — such as those used in the automotive
industries — and the acrylic-, epoxy- and polyester-based paints used during the preparation of “pre-coated” metal sheet.
NOTE 2 In some countries, the use of the term “plastics” as the singular form as well as the plural form is permitted.
3.2
scarification
shallow roughening of both metallic and plastic (including paint) surfaces, using either abrasion or blasting,
almost invariably improving the performance of the final bonded joint
4 Safety
Users of this International Standard shall be familiar with normal laboratory practice and the principles of good
industrial hygiene.
Users shall be aware that this International Standard does not purport to address all safety problems, and
it is their responsibility to establish practices which are compliant with relevant national health, safety and
environmental legislation.
Concentrated acids, alkalis and oxidizing agents (e.g. chromium trioxide, dichromates and chrome-based
solutions) are all highly corrosive chemicals. Splashes can cause severe damage to both skin and eyes and
will damage normal clothing. Protective clothing (e.g. overalls, gloves and goggles or visors) shall always be
worn when using these chemicals.
Similarly, appropriate precautions shall be taken when using solvents. At a minimum, eye protection and gloves
(or appropriate barrier cream) shall be worn.
Wherever possible, use propan-2-ol as a solvent. Otherwise, a ketone (acetone or methyl ethyl ketone) or,
though deprecated, a halogenated solvent, that meets the requirements of the Montreal Protocol and national
legislative requirements, can be used. Alcohols and ketones are flammable — particularly ketones. All such
materials are narcotic when concentrated. Ventilate properly, take account of vapour density and draw fumes
away from the operator.
Do not allow any cleaning materials to contact the skin. Abuse can lead to dermatitis.
Some of the methods given below employ dangerous techniques, materials and proprietary chemicals. It is
essential, therefore, that the supplier’s instructions be followed, health and safety data studied, and appropriate
safety procedures established.
Waste and spent materials shall be disposed of in accordance with national legislative requirements through
the services of an authorized disposal organization — whose advice shall always be sought.
WARNING — When making up solutions:
—  NEVER POUR WATER INTO ACID.
—  ALWAYS ADD ACID IN A SLOW, STEADY STREAM TO A STIRRED SOLUTION.
An exothermic reaction can heat the resulting mixture. If this occurs, contamination hazards will be
intensified. TAKE GREAT CARE.
5 Initial preparative techniques
5.1 General
When safety-critical structures are being bonded, optimum treatment is always necessary. This requires the
use of appropriate techniques to both clean and modify the surface, which itself can be either an inorganic or
an organic coating — or even a combination of both. By contrast, when joints are only to be lightly or nominally
loaded, the use
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