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"Black/Brown stains on electroless nickel plating"

Current question and answers:

November 16, 2020

Q. Hello.
I am working in a plating company. I am quality assurance assigned to electroless nickel, with aluminum as base metal.
We'd had this problem since our early start up until now whereby we encounter unremovable black stain usually on holes of parts. These black stains will occur when our MTO reaches 1.0 and beyond, but is not consistent. Affected area is low thickness compared to other good areas. We use nickel sulfate solution and our reducing agent is sodium hypophosphite. All the monitoring parameters such as pH, temp., dipping time, concentration were controlled. We were thinking that it was air trapped during plating and was being oxidized. Kindly recommend what step we should do to eliminate the black stain.
Thank you.

Antoine Ambaloc
- Cavite, Philippines
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November 18, 2020

A. Hi, Antonie,

I think first thing first is to verify those black stain area is EN plated or not. For aluminum base material, there is a test called Alizarin test (hopefully it's the right spelling), you might remove those stains by water or IPA then conduct this test. Pink color indicating poor coating coverage.
You might update us once the test is done. Thanks.

Raymond Wang
- Singapore
^


January 14, 2021

A. Hi Antoine,
As suggested by Raymond, first you need to check if the black stain area is EN plated or not.
In my opinion it is more likely that the surface is nickel plated and then oxidized, because nickel oxide has a dark color, unlike aluminum oxide that is clear.
Black stains near holes, especially blind and threaded holes, are due mainly to insufficient rinsing after nickel. This usually happens on medium phosphorous electroless nickel, while high phosphorous tends to stain less.
Trapped air does not allow nickel to be deposited in the hole but should not lead to black spots.

Matteo Bordiga
- Soncino, Italy
^


Black Stain in blind and threaded Holes

January 15, 2021

Q. Hello
Hope all of us are doing well.
This is a continuation of what I've inquired about before:

I am working in a plating company. I am quality assurance assigned to electroless nickel, with aluminum as base metal.
We'd had this problem since our early start up until now whereby we encounter unremovable black stain usually on holes of parts. These black stains will occur when our MTO reaches 1.0 and beyond, but is not consistent. Affected area is low thickness compared to other good areas. We use nickel sulfate solution and our reducing agent is sodium hypophosphite. All the monitoring parameters such as pH, temp., dipping time, concentration were controlled. We were thinking that it was air trapped during plating and was being oxidized. Kindly recommend what step we should do to eliminate the black stain.
Thank you.

Antoine Ambaloc [returning]
- Cavite, Philippines
^


January 2021

A. Hi cousin Antoine. I was wondering why you posted this "continuation" as a new thread, then it hit me that perhaps you never received our notification about where your thread and the two responses offered could be found :-(

Hopefully you'll see it this time and be able to say "We conducted the Alizarin test, and ... " or "Although we were unable to do that Alizarin test because ..." :-)

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^

----
P.S: Although we receive notice if an e-mail address bounces, we don't get one if our response was filtered as spam. Readers who wish to participate should please start by 'whitelisting' mooney@finishing.com




Previous closely related Q&A's, oldest first:

2006

Q. Our company experiences a significant increase of material defects due to brown stain. We always thought that this is caused by high conductivity on water rinses. We maintain the conductivity of our rinses to less than 1 uS/cm. Still brown stain persists. Would there be any other causes of this problem?
Thanks.

JM Puguan
Plating company - Cavite, Philippines
^


2006

A. Suggest to:

1. Check if Ni bath metallic contamination such as Cu is high. If so, run dummy at 2-5 ASF for several hours;
2. Measure nickel thickness (too low?) and porosity (too high?)
3. Verify whether plating parts are completely dried after plating;
4. Storage condition such as temp and relative humidity is important also

David Shiu
David Shiu
- Singapore
^


2006

A. Brown spots causes are existence of Fe3+; mechanical contaminations; overdosage of brightener/leveling agent; or pH value is too high. Best regards,

Ada Garber
- Istanbul, Yurkey
^



2006

Q. We are experiencing a problem with brown staining/ tarnishing appearing a few hours later on radio components that we are electroless nickel plating . The components are machined from solid aluminium billets and are electroless coated for one hour using a high phosphorous solution. After plating they are rinsed in de-ionised water and then blown with compressed air to clear any blind holes , corners, etc.Does anyone have any advise for us ? We cannot use any de - watering or oil based coatings as some components are then powder coated afterwards .

MARK WRIGHT
electroplating - DURBAN, KZN, SOUTH AFRICA
^


2006

A. Hello Mark,
Can you pinpoint if the staining is coming from blind holes or corners on the part? If so, an air agitated DI rinse may be in order. I like to use a 2 to 3 counterflow rinse system with the last rinse being air agitated. As you probably know the last DI rinse should be the cleanest. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York
^


2006

A. I THINK FINAL DI WATER RINSE SHOULD BE HOT TEMP. 60-70 °C.
IMMERSION TIME 2 TO 3 minutes WITH AIR AGITATION.
THEN DRY HOT AIR, OIL-FREE

ajay raina
Ajay Raina
Ludhiana, Punjab, India
^


2006

A. Dear,

The quality of rinse water can cause brown stains. First make sure you use DM water for rinse. Second check silicate in rinse water. There are chemicals and color disk to check silicate in water. If you exceed 1 ppm of silicate, you are likely to get stains. A regeneration of DM plant will bring down silicate contamination. Check silicate and try. Best wishes.

Kaushik Magiawala
plating shop employee - Gandhinagar, India
^



Black stains formation on electroless nickel plating

December 15, 2008

Black stains formation on electroless nickel (MP) plated surface after two to three days.
Giving good pre-treatment and post treatment. After plating it shows good bright finish and with in one or two days it started to form the stains. Because of this we are facing a lot of problems. Please help us

Anil mehra
plating shop employee - Faridabad,Hariana
^


January 15, 2009

A. Hello Mr Mehra,

Looks like your EN bath has metallic or organic contamination somewhere. You need to find out its source and eliminate it. The contamination may also be from leaded steel parts; assuming all other process parameters are adhered to and you ae using a good process supplier.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind
supporting advertiser
Bengaluru, Karnataka, India

saify logo
^


January 16, 2009

A. Aluminum contamination will start out as a dull then gray then a dark gray/black EN coating. Lead will normally stop the plating.

James Watts
- Navarre, Florida
^



August 11, 2009

Q. We are having problem regarding rust in our plating on Fe material, we already increased our concentration on acids and plating thickness but still rust exists. What are the countermeasures do you suggest we should implement? Thank you.

Mie Leoveras
Plating Company - Cavite, Philippines
^


August 12, 2009

Hi, Mie. Are you from the same plating company in Cavite as JM Puguan, and is this a continuation of the same question? Several suggestions were already made. Can you frame your question in terms of those previous suggestions? Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



March 28, 2013

Q. Hi.
Actually my company produces the product from electroless nickel plating.
Currently my company also has same problem about the stain issue. Until now we also cannot solve this problem. We already do adjustment at rinsing tank, but still have stains. Can you advise me of the solution to avoid this problem.

Nur Zana
- Selangor, Malaysia
^


June 3, 2013

Hi cousin Nur.

Apologies, but nobody has replied to you yet. But if you have "the same problem" please read the suggestions for that problem

Please try to express your ongoing "same problem" in terms of those suggestions. Thanks! Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^

• Please see also thread 45977, "Electroless nickel plating is turning black, tarnishing"



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