Found Blue Green Rust in Bolt after Salt Spray Testing

[praveen011281]

Hi All,
We found Blue ,Green rust in Bolt after our Salt Spary Testing.
Test method is acoording to R16,Each test pieaces is hung by thread.
Surface Finish Spec:MfZn8-K(Black)
SST Spec: 96 hrs Min(White Rust) at 35degreec/5% nacl solution and 240 hrs (Red Rust)

Can any one of you guide why Blue Green Rust is occuring ??
Kindly advice me.

Thanks & Regards,
Praveen

 

[wmarhel]

Could there be copper in the bolt material, or possibly the salt spray unit was contaminated somehow? You might try a google search and see if anything pops up. But copper is the first thing that comes to mind.

Wayne

 

[praveen011281]

Could there be copper in the bolt material, or possibly the salt spray unit was contaminated somehow? You might try a google search and see if anything pops up. But copper is the first thing that comes to mind.

Wayne

Hi Wayne,
Thanks for your Input.
We also anticipate the same cause.
We checked SST chamber its pretty good !!
Can you pls suggest what could be the failure mode in surface finish process ?

How to prevent the root cause ?

Your input will be highly appreciated.

Thanks for kind understanding & Patience.

Praveen

 

[AndyN]

Could there be copper in the bolt material, or possibly the salt spray unit was contaminated somehow? You might try a google search and see if anything pops up. But copper is the first thing that comes to mind.

Wayne

I agree with Wayne - he beat me to the post. Do you have a chem. analysis for the bolt material? There are some fasteners around which are not always to the correct spec.

 

[bobdoering]

Don't forget to see if there was any copper from the plating or handling at the plating. I am not familiar with the black zinc surface finish to know if there is any copper in that system, but it would be a good thing to know - especially if there is a lot of blue or green oxidation. I agree - highest probability is copper salts. Nickel can be green, copper can be both - so, for kicks you might want to see if there is nickel and copper.

 

[Randy]

Copper, zinc...

Just go to a navy yard and check out the hulks.

 

[Sorin]

I assume is a contamination in the baths where the parts where processed for surface finishing.

 

[wmarhel]

Hi Wayne,
Thanks for your Input.
We also anticipate the same cause.
We checked SST chamber its pretty good !!
Can you pls suggest what could be the failure mode in surface finish process ?

How to prevent the root cause ?

Your input will be highly appreciated.

Thanks for kind understanding & Patience.

Praveen

First person I'd contact would be the bolt supplier. Explain the situation to them and send them some pictures. If there is a failure on this part, or any kind of abnormality, you need to get them involved. Perhaps the chemistry on the plating isn't incorrect and this is why your getting the unusual build-up.

Two things related to the salt spray equipment. Check with maintenance and the users to see if anything has been done to it lately or it has been acting funny. Also, check to see what other chemicals, if any, are in the vicinity. You don't happen to use any copper based products, such as copper sulfate, in any of your processes by any chance.

Wayne

 

[praveen011281]

Dear All,
Thanks for your valuable inputs,Let me investigate the real cause and update in the forum.
Tks
Praveen

 

[Umang Vidyarthi]

Hi All,
We found Blue ,Green rust in Bolt after our Salt Spary Testing.
Test method is acoording to R16,Each test pieaces is hung by thread.
Surface Finish Spec:MfZn8-K(Black)
SST Spec: 96 hrs Min(White Rust) at 35degreec/5% nacl solution and 240 hrs (Red Rust)

Can any one of you guide why Blue Green Rust is occuring ??
Kindly advice me.

Thanks & Regards,
Praveen

Hi Praveen,

Before answering you I have a few questions:

1. How dark is the bluish green rust? IMO it must be of a very very light shade.
2. How is the plating done, in tanks or in barrel?
3. Which chemical arer you using for black passivation?
4. Do you give a coat of lacquer in order to improve shelf life?

Umang