March 2015


Welcome to ‘Stainless Solutions’ from IMOA. Each month, we will cover a different stainless steel issue with tips on design and specification, and links to technical resources.  This month we are discussing stainless steel surface finish specification.
Stainless steel finish specification

Surface finish selection is critical to achieving aesthetic goals but it can also have a tremendous influence on corrosion performance and, even in less corrosive environments, dirt accumulation.

Finish options


Stainless steel finishes are available in a wide range of mechanically applied patterns, textures, and colors. Etched patterns are also available. It is not uncommon to combine techniques to achieve unique finishes. There are numerous resources to assist with aesthetic finish selection:


Corrosion performance


The relationship between surface roughness and susceptibility to corrosion of materials (i.e. not just stainless steel) is well known. Rougher surfaces accumulate more dust, debris and corrosive substances from the environment, such as industrial pollutants and coastal and deicing salts. Their higher surface tension means that they also retain the moisture that is needed for corrosion to occur for longer periods of time.

This relationship is discussed in Stainless Steel and the Challenge of Time, EuroInox and Guidelines for Corrosion Prevention, Nickel Institute.

Textured finishes (i.e. coined and embossed) are slightly different than other rougher surfaces, consisting of patterns pressed into the surface. Typically, the underlying surface is a very smooth 2B or BA mill finish, which inherently retains fewer deposits. The ability of the chosen pattern to be easily rain-washed needs to be assessed.

Specifying low sulfur austenitic stainless steel (e.g. 316) sheet, strip and plate is important for both appearance and corrosion resistance - see Stainless Steel: A Perfect Mirror Finish, The Construction Specifier.

IMOA has developed a scoring system and case studies to provide guidance with finish and alloy selection -see Which Stainless Steel Should Be Specified For Exterior Applications, and the links to information sources on different corrosion environments.

Specifications


It is important to use internationally recognized finish specifications. They provide legal protection for the buyer and seller and help to more clearly define requirements. However, specifiers must understand that standards describe how finishes are applied but do not provide enough detail to ensure consistency.

Specifiers therefore need to work closely with suppliers to precisely define the finish using parameters such as surface roughness range, reflectivity (gloss), and more specific aspects of appearance, such as color range. Visual standards must be agreed by suppliers and matched for aesthetic applications. Many special finishes are not covered by standard specifications and should be described in as much detail as possible. For further information, see IMOA/Nickel Institute International Specifications, Guidelines and Industry Associations list.

Finish measurement resources

Stainless Solutions e-newsletter archive

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Continuing Education – American Institute of Architects (AIA)

IMOA is an AIA continuing education system approved provider with eight 1-hour programs that are registered for both live face-to-face and distance learning credit.

1. Stainless Steel Sustainable Design
2. Bioclimatic Design With Stainless Steel Weather Screens
3. Stainless Steel Structural Design
4. Stainless Steel Specification For Corrosive Applications
5. Deicing Salt: Stainless Steel Selection to Avoid Corrosion
6. Stainless Steel Finish Specification
7. Advanced Stainless Steel Specification and Problem Avoidance
8. Specification of Stainless Steel Finishes and Grades For Corrosive Applications

For more information or to schedule a workshop contact Catherine Houska, 412-369-0377 or email chouska@tmr-inc.com.

What is IMOA?

IMOA (International Molybdenum Association) is a non-profit industry association, which provides technical information to assist with successful specification of molybdenum-containing materials. Molybdenum is an element. When it is added to stainless steel, molybdenum increases its resistance to corrosion caused by deicing salts, coastal atmosphere and pollution.

If you have a topic suggestion for a future issue of Stainless Solutions or need additional technical advice on stainless steel specification and selection, please get in touch here.

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Disclaimer

In providing consultation or other assistance with respect to technical issues, any consultation, assistance or material is provided for the general information of the recipient and should not be used or relied upon for any specific application without first securing competent advice. IMOA and their respective employees, consultants and members (i) make no representation or warranty, express or implied, of any kind with regard to such consultation, assistance or material including no representation or warranty of  suitability for any general or specific use; (ii) assume no liability or responsibility of any kind in connection  therewith; and (iii) disclaim any and all liability for any claim that arises therefrom. 

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