June 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 the fundamentals of using recognized standards for stainless steel specification.
Stainless Steel Specifications & Guidelines

Properly specified stainless steel can last the life of a building or structure with only minimal maintenance cleaning.  Unfortunately, many project specifications are incomplete which can lead to unexpected failures.

In upcoming issues, Stainless Solutions will address common specification problems in more detail.  This issue focuses on fundamental specification issues and the importance of using internationally recognized stainless steel specifications and guidelines.

IMOA and the Nickel Institute have developed a list of widely used international specifications and guidelines. It is regularly updated so please check our website for the latest version.

International Specifications, Guidelines & Industry Associations

International list of widely used stainless steel product, material and welding standard specifications, structural design resources, basic rules and resource sites.  Stainless steel industry association contacts are provided to assist with country specific specifications

Download PDF (394 K, English)

Fundamental Rules


Complete specifications are critical for communicating requirements. They can always be tightened and still be legally binding, but not relaxed. These are the most important rules, others can be found in our list.

1. A standard (ASTM, EN, JIS, etc.) or guideline from an internationally recognized standard setting body should always be used to specify the alloy, mechanical and physical properties, tolerances (aesthetic, flatness and dimensional) and other requirements.

2. Industry and professional association brochures are not standards and are therefore not legally binding. Text can be extracted and used to create a project specification but they should not be referenced like standards.

3. Suppliers should be required to provide the mill certifications for all of the stainless steel and, if applicable, the weld filler metal used. This helps to ensure compliance and provides material traceability.

4. A legally binding alloy designation such as UNS or EN number should be used to designate the specific alloy chemistry. No stainless steel AISI numbers (304, 316, etc.) have been issued for about 40 years and they are too general. Identifiers like “18-8” are even less precise and that can lead to problems. If there is a common name like Type 316L, use both it and the UNS or EN number (i.e. 316L /UNS S31603 or EN 1.4404). There is further guidance in our Stainless Steel Selection pages.

5. Unlike mill and polished finishes (i.e. No. 3, 4, 7, 8) which are described in industry standards, many aesthetic finishes are not and must be described and quantified as much as possible in project specifications. Read more about Finish Specification.

6. Minimum, maximum or thickness ranges should be specified in inches or mm. Stainless steel “gauges” are not defined by industry standards. Without a specific thickness, you have no legal protection.

7. “L” after AISI numbers mean lower carbon content. It only needs to be specified when an austenitic stainless steel (i.e. 304L (UNS S30403) or 316L (UNS S31603)) that is 0.125 inch (3.175 mm) or greater in thickness will be welded. Other than the welded area, carbon has no effect on corrosion performance.

8. Sulfur content affects both the appearance and corrosion resistance of austenitic stainless steels. Sheet, strip and plate can be specified as low sulfur. Bar, tube and pipe will have higher sulfur levels and should be chemically passivated to remove surface sulfides after fabrication. See the ASTM A240 notes.

9. Pickling, electropolishing and/or grinding is required to restore corrosion resistance after welding or when there is deeply embedded carbon steel from fabrication. Specifiers should require compliance with ASTM A380 or a comparable international standard. Read about Cleaning and Installation and about fabrication of Austenitic and Duplex stainless steels.

10. If the stainless steel has a higher sulfur level, if iron contamination during fabrication is likely, or if your surface finish is rough, you should require chemical passivation after the final fabrication and finishing. If you are using ASTM standards, then A967 is the correct specification.

Embedded iron was not sufficiently removed by the fabricator’s chemical passivation. Grinding and pickling are needed.

Photo C. Houska, TMR Consulting.

Welded Type 316L (UNS 31603, EN 1.4404) railings that were pickled, ground and polished to a very smooth finish to resist deicing salt corrosion.

Photo C. Houska, TMR Consulting

Stainless Steel Library

Download a free Stainless Steel Library (zip file, 390 MB) with over 280 pdfs covering building and construction applications, selection, specification, fabrication, sustainability and other common questions.

Stainless Solutions e-newsletter archive

For previous issues or to subscibe to the e-newsletter, please visit the archive page.

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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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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