preface
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The committee responsible for this document is ISO/TC 156, Corrosion of Metals and Alloys.

ISO 18069-2015 “Corrosion of metals and alloys — Method for determining uniform corrosion rates of stainless steel and nickel-based alloys in liquids”

introduce
Stainless steel and nickel-based alloys generally have good corrosion resistance, but uniform corrosion occurs in acidic and alkaline solutions. Uniform corrosion rates in aqueous solutions are generally considered to be a fairly stable process as long as the corrosive environment is constant in terms of chemical composition, temperature, and flow conditions. Therefore, uniform corrosion resistance of stainless steel and nickel-based alloys is usually determined by short-term laboratory sample immersion tests conducted under controlled conditions. However, in practical applications, the conditions of service may change somewhat, which may result in temporary activation of the surface of stainless steel or nickel-based alloys. Changes in temperature, fluctuations in air or other oxidants, exposure to less valuable materials (such as mild steel) or certain cleaners are all factors that may lead to activation in some cases.

Therefore, an important property to be studied is the ability of the material to passivate after activation, so the method includes activation of the sample. The corrosion rate determined by this test can be used as a basis for material selection and material life estimation.

1 range
This standard specifies the expected corrosion rate of uniform corrosion of stainless steel and nickel-based alloys in liquids and the ability of materials to passivate after activation.

The method is intended to be used to estimate uniform corrosion rates of liquids under atmospheric conditions, chemical industry under specific environmental conditions, and not as a qualification test. It can also be used to determine isoetch graphs and temperatures where corrosion rates exceed 0.1mm /a.

This standard does not apply to excessive corrosion rates exceeding 1 mm/a, as higher corrosion rates indicate that stainless steel is not suitable for application.

This standard does not apply to solutions containing halides, especially chlorides, which may cause localized corrosion.

2 Normative references
All or part of the following documents are referred to normatively in this document and are not available for their use. For dated references, only the quoted version applies. For undated references, the latest version of the reference applies.

ISO 3696, Analytical laboratory water – specifications and test methods

ISO 8044, Corrosion of metals and alloys – Basic terms and definitions

ISO 17864, Corrosion of metals and alloys – Determination of critical corrosion temperature under potentiostatic control

3 Terms and Definitions
For the purposes of this document, the terms and definitions given in ISO 8044 apply.

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