Immersion Corrosion Test — ASTM G31 / ISO 11130

What Is Immersion Corrosion?

The immersion corrosion test is one in which the sample is immersed in a defined solution for a specific duration, and the corrosion rate is calculated from mass loss. It is used to assess general (uniform) corrosion resistance.

Purpose of Immersion Corrosion

The purpose is to determine a material's corrosion rate in a specific process fluid or service environment, and to support material selection.

Which Products Is Immersion Corrosion Applied To?

Chemical process equipment materials
Pipe and tank materials
Heat exchanger components
Marine environment hardware

In Which Sectors Is Immersion Corrosion Used?

AutomotiveMetalSteelConstructionMaritime

Standards Related to Immersion Corrosion

ASTM G31
ISO 11130
NACE TM0169
ASTM B117tuz sisi (salt spray) korozyon testi test
ISO 9227tuz sisi korozyon testi test
ASTM G85modified salt fog (cyclic) test test
ASTM G48pitting and crevice corrosion in stainless steels test
ISO 16701cyclic corrosion test test
ISO 6270strength in condensation environment test
SAE J2334cyclic laboratory corrosion testing test
VDA 233-102cyclic corrosion testing in automotive test

Immersion Corrosion Conditions

Solution: Actual process fluid or solution defined in the specification
Temperature: Service temperature or standard defined constant temperature
Solution/sample ratio: Minimum volume/area ratio defined in ASTM G31
Ventilation: Ventilated or ventilated (deoxygenated) condition is indicated

Equipment for Immersion Corrosion

Temperature-controlled immersion setup with reflux condenser
Sample suspension fixture (insulating)
Precision balance
Fume hood

Sample Requirements for Immersion Corrosion

Sample surface area must be measured and recorded
The surface must be cleaned per the standard
Initial mass must be measured on a precision balance
Generally at least three specimens

Duration of Immersion Corrosion

Ranges from days to weeks depending on the specification. ASTM G31 recommends interim measurement for long-duration tests.

Immersion Corrosion Procedure

1Sample surface area and mass are measured.
2The solution is prepared and brought to temperature.
3The sample is immersed in the solution on an insulating support.
4The conditions are maintained for the defined duration.
5The sample is removed and corrosion products are cleaned off per the standard.
6Mass loss is measured and corrosion rate calculated.

Immersion Corrosion Acceptance Criteria

The acceptance criterion is given in the specification as maximum corrosion rate (mm/year or mpy).

Evaluation of Results

Corrosion rate is calculated from mass loss, surface area and duration. The surface is also examined for localised corrosion (pitting, crevice); if present, the average rate is misleading.

Immersion Corrosion Report

Standard applied
Solution composition, temperature and aeration status
Sample surface area and duration
Mass loss and calculated corrosion rate
Localised corrosion observations

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

Chemical process equipment specifications

Corrosion Tests — What Does This Testing Field Cover?

The section below describes the field that the Immersion 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 Immersion Corrosion

According to which standard is Immersion Corrosion made?

Immersion Corrosion is executed in scope ASTM G31, ISO 11130 and NACE TM0169. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.

Which products does Immersion Corrosion apply to?

Mainly applied to Chemical process equipment materials, Pipe and tank materials, Heat exchanger components and Marine environment hardware. Whether your product is included in the scope is determined by examining its technical specifications and intended use.

Under what conditions is Immersion Corrosion done?

The determining parameters are: Solution — Actual process fluid or solution defined in the specification, Temperature — Service temperature or standard defined constant temperature and Solution/sample ratio — Minimum volume/area ratio defined in ASTM G31. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.

What kind of sample is needed for Immersion Corrosion?

Sample surface area must be measured and recorded, The surface must be cleaned per the standard and Initial mass must be measured on a precision balance. The number of samples is determined according to the product standard and the scope to be reported.

How long does Immersion Corrosion take?

Ranges from days to weeks depending on the specification. ASTM G31 recommends interim measurement for long-duration tests. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.

What is the Immersion Corrosion result called "appropriate"?

The acceptance criterion is given in the specification as maximum corrosion rate (mm/year or mpy).