Cyclic Corrosion – VDA 233-102

What Is Cyclic Corrosion — VDA 233-102?

The cyclic corrosion test is an accelerated corrosion test in which wetting, drying, humidity, and sometimes low-temperature stages are applied in cycles instead of continuous salt fog. It gives results closer to the actual atmospheric corrosion mechanism.

Purpose of Cyclic Corrosion — VDA 233-102

The purpose is to assess the effect of wet-dry transitions, which continuous salt fog does not represent, and to provide better correlation with field behaviour.

Which Products Is Cyclic Corrosion — VDA 233-102 Applied To?

Automotive body and chassis components
Painted and coated sheet metal parts
Fasteners
Outdoor building components

In Which Sectors Is Cyclic Corrosion — VDA 233-102 Used?

AutomotiveMetalSteelConstructionMaritime

Standards Related to Cyclic Corrosion — VDA 233-102

VDA 233-102cyclic corrosion testing in automotive test

Cyclic Corrosion — VDA 233-102 Conditions

Cycle structure: The order and duration of the wetting, drying and moisture stages defined in the specification
Solution: Dilute electrolyte or NaCl solution according to specification
Temperature: It varies depending on the stage; some specifications include a low temperature phase
Number of cycles: Defined in specification (e.g. 30, 60, 90 cycles)

Equipment for Cyclic Corrosion — VDA 233-102

Programmable cyclic corrosion chamber
Solution preparation and spray system
Humidity and temperature control system
Data logging system

Sample Requirements for Cyclic Corrosion — VDA 233-102

Generally at least three specimens
Pre-damage by scribe or stone-chip impact may be applied per the specification
Cut edges must be masked
The coating system and thickness must be recorded

Duration of Cyclic Corrosion — VDA 233-102

Depends on the number of cycles. One cycle typically takes 8 – 24 hours; a 60-cycle programme takes weeks.

Cyclic Corrosion — VDA 233-102 Procedure

1Samples are prepared and pre-damage applied if required.
2The cycle programme from the specification is loaded into the chamber.
3Wetting, drying and humidity stages are run in sequence.
4Interim observations are made at defined cycle intervals.
5Once the programme is complete, samples are washed and evaluated.

Cyclic Corrosion — VDA 233-102 Acceptance Criteria

The acceptance criterion is defined in the specification; usually given as maximum corrosion spread around the scribe or maximum under-film corrosion width.

Evaluation of Results

Scribe spread, blistering and base-metal corrosion are measured. Cyclic results are not comparable with continuous salt spray.

Cyclic Corrosion — VDA 233-102 Report

Applied standard and cycle programme
Solution composition and stage durations
Number of cycles and interim observations
Corrosion spread measurements
Photographs

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Automotive OEM corrosion specifications (VDA, SAE)

Corrosion Tests — What Does This Testing Field Cover?

The section below describes the field that the Cyclic Corrosion test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Corrosion testing assesses under accelerated conditions how long metals and coatings last in a corrosive environment. The family contains two approaches, and the difference between them is the most important knowledge in the field: constant-condition tests and cyclic tests.

Constant-condition salt spray (ASTM B117, ISO 9227) maintains the same environment in the chamber throughout: the same salt concentration, the same temperature, a continuously wet surface. The strength of this approach is its REPEATABILITY; because the conditions are tightly defined, results from different laboratories come out close to one another. That is exactly the property wanted when monitoring production consistency and comparing suppliers.

But the real atmosphere is not constant. A surface gets wet, dries, warms, cools, takes UV and becomes soiled. The wet-dry cycle changes the corrosion mechanism: during drying the salt concentrates, oxygen access increases and corrosion accelerates. The form of damage on a continuously wet surface differs from that on a cyclically wetted one.

Cyclic tests (SAE J2334, VDA 233-102, ASTM G85, ISO 16701) imitate this variability and give results closer to the damage patterns seen in the field. The automotive sector has largely moved to this approach. The practical consequence is this: the same two coatings may RANK DIFFERENTLY in constant and cyclic tests; which test was applied determines the result.

No test in this family defines a DURATION OR ACCEPTANCE CRITERION. How many hours it is applied for and what level of damage is acceptable come from the product standard or the customer specification. The assessment scales are defined in separate standards: different scales are used for degree of rusting, blistering, creep from a scribe and loss of adhesion.

The damage looked for varies with the coating type. For metallic coatings, white rust (corrosion of the coating itself) and red rust (corrosion reaching the base metal) are reported separately, and specifications usually give a separate duration for each. On painted surfaces, creep from a scribe and blistering come to the fore.

Electrochemical methods are a separate body of work and answer a different question. Potentiodynamic polarisation, electrochemical impedance spectroscopy and pitting potential measurements reveal the MECHANISM and rate of corrosion within hours; chamber tests give the result visually over weeks. The two are complementary rather than alternatives.

Stainless steels have a special sub-body in the field: pitting and crevice corrosion and intergranular corrosion tests indicate the quality of the heat treatment and the condition after welding.

Method groups in this field

Constant-condition salt spray
ASTM B117 and ISO 9227 (NSS); for repeatable comparison and process control.
Acidified and accelerated
The AASS and CASS conditions of ISO 9227; preferred for decorative chromium-nickel coatings.
Cyclic corrosion
SAE J2334, VDA 233-102, ASTM G85 and ISO 16701; approaches field behaviour through wet-dry cycles.
Humidity and condensation
Steady damp heat, condensation and cyclic humidity tests; these reveal coating blistering.
Electrochemical
Polarisation, impedance spectroscopy, pitting and crevice corrosion potential measurements.
Stainless steel specific tests
Pitting and crevice corrosion, intergranular corrosion; indicators of heat treatment and weld quality.
Assessment scales
Scales for degree of rusting, blistering, creep from a scribe and loss of adhesion; the ratings come from these standards.

Commonly confused in this field

Chamber hours cannot be converted into field life; there is no reliable conversion factor.
Constant and cyclic tests can produce different rankings; whichever the specification states is the one applied.
A corrosion report without a stated duration and acceptance criterion cannot be interpreted.
If the coating thickness is not reported, the result cannot be compared; thickness directly affects durability.
White rust and red rust say different things; the two must be reported separately.
The position and angle of the specimen in the chamber affect the result; standards govern this and the report must document it.

Which decisions these results support

Selection of the coating system and supplier approval
Process control of the coating line and lot acceptance
Evidence of durability for automotive and outdoor products
Assessment of field corrosion damage and warranty decisions
Verification of heat treatment and weld quality in stainless steel

Related Tests

Frequently Asked Questions About Cyclic Corrosion — VDA 233-102

Why is the cyclic corrosion test preferred?

Continuous salt spray does not include wet-dry transitions and can mispredict field behaviour for some coating systems. Because cyclic tests include a drying stage, they correlate better with actual atmospheric corrosion.