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topic 57020

Criteria to decide if component passed or failed Salt Spray Test

A discussion started in 2011 but continuing through 2018

April 11, 2011

Q. I am having some difficulties in determining the conclusion from a salt spray test.
Is there any guideline to determine the acceptance of the rusty area? Such as location of the rusty area from edges or holes. Also have a hard time to determine the acceptance criteria for screw where the area is very small and there is much knurling and threading at screw.
Please help

Husri Hussain
QA Manager - Bayan Lepas, Penang, Malaysia

April 12, 2011

A. Hi, Husri.

Usually components are plated or processed per a recognized specification and that specification often contains its own rules for how to determine whether a component passed the salt spray test. Look at the specification you are plating this hardware to -- that is the first place to look for the acceptance criteria. Good luck.


Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 12, 2011

Q. Thanks Ted.
I am looking more on the guideline to determine if the rust occurs. Has there be a guideline which is widely used to determine which surface to be look at and which should not when looking at the rust area.
Rust to be inspected 1 mm from the cutting edges
Not to check on the hole area
Not to check at indentation area
Not to check at groove area

I am also in particularly looking on how to inspect the bolt, nut and screw for rust. Any idea what surface/area that one needs to look at. Thanks.

Husri Hussain [returning]
- Penang, Malaysia

A. Hi again Husri. Tell us the plating specification please! You continue with the assumption that all plating and metal finishing salt spray performance is evaluated per some non-specified but generally accepted parameters; you might be correct, but I do not think so.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 12, 2011

A. Dear Husri,

Maybe you can refer to ASTM B117 [link by ed. to spec at TechStreet] and ISO 9227 [link by ed. to spec at TechStreet].


CS Leong
- Selangor, Malaysia

October 2016

A. Hi CS. I don't think so. ASTM B117 tells you how to run a salt spray test, but not how to evaluate the result.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

November 5, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear

We have observed problem of black spots on threaded portion of bolt after 36 hours of salt spray testing. Is this a failure? What exactly can be considered as a failed fastener (bolt) as far as salt spray is considered?

Rajesh Verma
Engineer - Noida, U.P., India

November 8, 2011

A. Hi, Rajesh.

Although the salt-spray testing specification doesn't describe what constitutes passing or failing, the bolts were presumably plated to some particular plating specification. That specification often includes the evaluation criteria to decide whether the parts passed testing or not. We appended your posting to a similar thread, so please look at the previous answers. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

October 16, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi,I want to know about acceptance criteria used in Salt spray test. Whether red rust & white rust considered in welding area of coated part?

Manoj Jadhav
- Pune, Maharashtra, India

October 17, 2016

? Hi Manoj,

Difficult to answer your question as you have not given us enough details. Are you a specifier (deciding what you want for a pass/fail criterion) or a supplier of plated products or maybe a customer of plated parts that are illustrating corrosion issues?

I would guess you are a zinc plater or specifying zinc plate and want to understand the validity of corrosion appearing on plated welded joints. Of course this is purely conjecture as more detail is needed.

Brian Terry
Aerospace - Yeovil, Somerset, UK

October 21, 2016

A. Salutations,

This is regarding the usage of ASTM standards for evaluation of corrosion resistance.

ASTM B117 is a common standard to perform the test, but the evaluation of plating normally requires another ASTM standard.

For example, ASTM F1941/F1941M [link by ed. to spec at TechStreet] helps specify where you should evaluate white / red rust (such as the top of a bolt, side of a nut, etc) after a set number of hours based on the coating type (zinc, zinc nickel, etc) and thickness.

Another example would be ASTM B633 [link by ed. to spec at TechStreet] which describes how electrodeposited zinc on iron / steel should last based on thickness of zinc (i.e. service condition) and type of supplemental coating and is generally used for things larger than fasteners such as brackets or sheets. (There are other standards for Zinc - Nickel, Electroplated Nickel, and would recommend consulting your supplier)

Will do what I can to answer any follow up questions regarding validation of plating / organic coatings using ASTM B117.


Erick Leong
- Buffalo Grove, Illinois, USA

November 29, 2018

Q. According to ASTM B633, part is deemed acceptable if the white rust is 6mm or less from the edges from the edges of the specimen at the end of salt spray testing. But, my specimen is a M6 X 12 mm flange bolt. Looking at the specimen after testing, the white rust is less than 6 mm from the edges. Can the part be accepted?

Al Fauzi
- Johor, Malaysia

December 4, 2018

A. Hi Al,

You should talk with your client so he (with some technical basis) can say what is acceptable. We had some clients who didn't accept any rust after the SST, and some who accepted up to 5% rust (but no more) at the end of the test.

In small parts it is difficult to make an acceptance criteria, but it should be written in some technical document.

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

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