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topic 22800

Equivalence between ASTM B-117 vs. ISO 9227 NSS

A discussion started in 2003 but continuing through 2019


Q. We have a customer, that we supply some zinc electroplated mechanical components to. He requires at least 300 Hr Salt Spray according to standard ISO 9227 [link by ed. to spec at TechStreet].

Our finishing supplier gives us a 96 Hr Salt Spray BUT according to the standard ASTM B117 [link by ed. to spec at TechStreet] .

Is there any equivalence between this two standards ? Could this 96 hr (ASTM B-117) be the same as the 300 hr (ISO 9227 NSS) that my customer requires of me ?

I'll really appreciate your help....




A. Hi Sergio, ASTM B-117 does not address corrosion behavior of test specimens, but describes the parameters for conducting a salt spray test. So if you want to know how to set up a salt spray cabinet or how to make the salt solution, then B-117 is a reference. But benchmarking performance is something altogether different. I suggest that you send some parts out for testing according to the ISO standard to see if they meet the spec. That's the only way to know for sure.

George Gorecki
- Naperville, Illinois


A. ASTM B 117 and ISO 9227 are essentially the same-- standard specifications for conducting corrosion testing. ASTM B 117 is specific to neutral salt spray, whereas ISO 9227 also covers acetic acid (AASS) and copper acetic acid (CASS) tests. Conventional electroplated zinc (9 micrometer thickness) that is subsequently coated with a yellow chromate conversion coating typically produces less than 5% red rust after 96 hour salt spray testing. In order to meet the same % red rust for 300 hours of testing, you will need to do something different. Options include the following:

1. Thicker zinc plating (12+ micrometers) with a thicker chromate (olive green instead of yellow)
2. A sealer over the existing zinc plating + yellow chromate
3. Something totally different like zinc-alloy plating, organic coatings, etc.

Toby Padfield
- Troy, Michigan

October 2, 2010

Q. Hello. A personal good afternoon to all, I am Jose of Curitiba, I am a painting inspector, I am a specialist in the area of Salt Spray, and have a problem and knowing of the competence of all readers in corrosion, perhaps they can help me. I am needing to know if a gradual table of corrosion in assay exists of Salt Spray, if this table exists and if anyone would be able to post it, I will be thankful. Thanks a lot.

Jose Nunes
inspetor de pintura - Curitiba, Parana, Brazil

March 16, 2012

Q. I will be using ISO 9227 for testing our Component, standard test duration is 1440 hrs of NSS test.
Is it possible to reduce test duration by some accelerated Testing? Any ISO standard is available for this Testing?

Sagar R.
- India

March 16, 2012

A. Hi, Sagar.

As Toby mentions, ISO 9227 includes CASS testing, which is more aggressive than neutral salt spray. But which, is any, accelerated test is appropriate depends on what the finish is, and what you hope to test against. Remember that accelerated testing is not a proper indication of real world performance. Good luck.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

May 20, 2014

Q. Dear sirs, could you inform me please if there are any difference between standards ISO 9227 and ASTM B117? We did tests of our products under ISO 9227. Our competitors declares surface protection under ASTM B117. Could you inform me please, if ASTM B117 is easier to meet the requirements?
Many Thanks.

David Grusak
- Vrchlabi, Czech republic

simultaneous May 21, 2014

A. As far as I know, there isn't much difference between ISO9227 and B117, just the temperature accuracy in testing chamber is 35+-2 °C in B117, while it's 35+-1 °C in ISO9227.

Davey Shaw
Shenzhen, Guangdong, China

May 22, 2014

A. Hi David,

There are several differences between the two specifications, including salt concentration range, salt analysis, water quality, angle of inclination of test panels, corrosivity requirements, I think the temperature is about the only thing that has been standardised.

Your best bet is to get hold of a copy of ASTM B117 and do a gap analysis between the ISO and the ASTM. You will then need to talk to your customer about the possibility of using one specification in lieu of the other.

Brian Terry
Aerospace - Yeovil, Somerset, UK

May 26, 2014

thumbs up signDear Brian and Davey,
Thank you very much for your answers. I appreciate it! So I will start with benchmark with these two standards.
Thank you.

David Grusak [returning]
- Vrchlabi, Czech republic

October 6, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. What is major difference between ISO 9227 [link by ed. to spec at TechStreet] & ASTM B117 [link by ed. to spec at TechStreet] excepts to temperature?

Neeraj Rao
- New Delhi India

October 2018

A. Hi Neeraj. Brian Terry has directly answered your question, but please post your situation rather than an abstract question so that readers can best help you. Thanks.

What do you want to test? ... because the specs you mention have to do with how to design and operate a salt spray cabinet; generally the plating, painting, or other metal finishing spec for your components tells you how to test them and how to interpret the results of the tests. A requirement that a component 'pass' an accelerated corrosion test isn't often meaningful until the finishing spec tells you what that means :-)

Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

February 12, 2019

Q. Hello I've been tasked with finding the main difference between the testing standards "ASTM B-117" and "EN ISO 9227" by my director.

Our issue is that we have a coating of Heresite which is suitable to 6000+ hours according to ASTM B-117. However our main supplier occasionally has supply chain issues and has recommended us an alternative which suffers a break down at 1500 hours according to EN ISO 9227.

Obviously as our supplier they wouldn't recommend us a product that is considerably less efficient than what we are already getting -- are we missing something?


Oliver Tennant
Kelvion - Fareham, Hampshire, UK.

February 2019

A. Hi Ollie. Do you have both specs in your possession? If you do, you should be able to understand what Toby has been telling us: that ASTM B117 [link by ed. to spec at TechStreet] covers only one type of test, Neutral Salt Spray; different ASTM standards are used to call out other salt spray tests like AASS ( ASTM G85 [link by ed. to spec at TechStreet]) and CASS (ASTM B368 [link by ed. to spec at TechStreet]) ... whereas ISO 9227 covers all three.

ASTM apples are fairly close to ISO apples, but not to ISO oranges. Are you certain that the 1500 hour ISO rating is for Neutral Salt Spray? If so, which is probably the case, you're pretty close to comparing apples to apples, so the finishes don't sound equivalent if one lasts 6000+ hours in NSS and the other fails at only 1500 hours. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

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