Aloha, fun & authoritative answers -- no cost, no registration, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Home /
Site 🔍
pub  Where the
world gathers for metal finishing
Q&As since 1989


Questions about zinc electroplating specification Fe/Zn8

this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q. When ASTM B633 specifies SC2 (Fe/Zn8) does this mean a minimum or an exact? Can the supplier send us material with a range of 8-12 microns with the 9-12 microns having a deposit build up which interferes with the functionality of our part?

Janice Tessier
- Sealy, Texas

A. To the best of my knowledge, the thickness is the minimum. It would be very difficult to obtain a certain thickness exactly, for example 8 microns. We need to have a range on the thickness.

You could specify also a maximum thickness, and work with your supplier to see if it is possible to work on this range.

I hope this helps.

Enrique Segovia
- Monterrey, Mexico

A. Hello Janice,

Is the product that you are having a problem with a fastener? The spec. Fe/Zn 8 calls out a minimum specification (0.00031") for zinc on steel, I believe. However, a standard 2A/2B thread fit only has an allowance for finishing of 0.00025". If the plater is trying to meet the intent of the specification which you have called out, and the fastener is relatively long, it is very possible that there will be enough zinc on the starter thread to cause a thread interference. The same issue can occur on a stamping with a threaded hole.

Hope that this helps.

Best regards,

Brian A. Calver, CEF
- Grimsby, Ontario, Canada

A. You could specify the maximum thickness allowed for Fe/Zn 12 classification.

Thiagaraj Maruthi
Engineer in conveyor manufacturing - Kluang, Johor, Malaysia
March 31, 2010

Zn6 with passivate bi-chromatic

Tutorial for newbies:
(to hopefully help readers more quickly understand the Q&A's)

Many questions here ask about Spec "MFZnxx etc.". But these are not specifications, they are codes within an unspecified specification. Trying to determine the meaning of a code without knowing what spec it is found within will not work at all :-(
For a quick example, the meaning of the "8" in code MFZn8 in certain specs is "8 micron thickness". But the meaning of "2" in code MFZn2 in other specs is "class 2" -- it certainly does not mean 2 microns thickness (less than 0.0001")

Q. We have had a request regarding ZN 6 Passivate Blue. What does the 6 mean?
Why Blue over gold or clear?

Also what is passivate bi-chromatic?

Are there any links to good websites describing the finishes and passivation process?

David Lovegrove
Product Design - Christchurch, New Zealand

A. David,

ZN6 passivate blue is zinc plating with blue passivation using hexavalent chrome.
Now since hexavalent chrome is being phased out, blue passivation with trivalent chrome process is commercially available which is superior to dichromate type hexavalent chromium process. The neutral salt spay life before white rust as well as the finish is better than the latter.

However, yellow iridescent passivation (what you are referring to as "gold") has better corrosion resistance than blue passivation ("clear.")

- Mumbai, India

A. Zn6 is 6 microns of zinc.

John Martin
- Wales

! I have read your question and read the answers. I must admit both could be correct. I think you need to go back to your customer and ask him exactly what he wants. It is a problem in the plating game when a customer gives a "spec" like that (internal spec) that is not clearly understood by the plater.

gary joseph
Gary Joseph
South Africa

Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)

Q. We are quoting a electroplate spec and want to better understand the "breakdown" of the spec. Ep-Fe/Zn8/CM2.

Kim Hewitt
Metal Stamper - Fraser Michigan

A. Ep : electroplate
Fe : substrate to be plated
Zn : kind of plating
8 : thickness (8 mic)
CM1 : blue chromate
CM2 : yellow chromate

Joko P. Yuniartanto
- Bekasi, West Java, Indonesia
May 11, 2009

A. Hi Kim. Hopefully Joko's reply answered your question satisfactorily. Still I would warn that several different zinc plating specs might include similar codes like Fe, Zn8, and CM2, while including additional requirements about testing, lot size, etc. So you probably should be careful to call it out as "ASTM spec. no xxxx type Fe/Zn8/CM2" or "ISO xxxx type Fe/Zn8/CM2" or "Nissan xxxx type Fe/Zn8/CM2" or whatever is the case :-)


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

What is Fe/Zn 5 c 2C F-010

Q. I have a customer drawing that states on the finishing field the follows:
ZINC PLATE Fe/Zn 5 c 2C F-010.
As far as I know this is a Zinc Plating over steel, 5 microns, chromate; however I don't know what the rest of the spec. means "2C F-010".
Could somebody help me with this?

Julio Espinoza
Plexus Electronic Assembly - El Paso, Texas

A. Can't you go back to your customer and ask what body issued the standard?

It has the look of a European standard but is not written in the manner which the relevant standard, BS EN 12329 demands. [ed. note: that spec has been superceded by BS EN ISO 2081]

John Martin
- Wales

A. That is part of ASTM F1941/F1941M-16

FE/ZN = Zinc, 5 = .0002 Min thick, C = Yellow

Matt Kelly
- Wheeling, Illinois, USA
June 1, 2012

Q. According to my customer's drawing, it requires surface treatment: Fe/Zn 8 C5. I don't know what "Fe/Zn 8 C5" means. Please inform me if somebody knows, thanks.

Claire Hsieh
exporter of fasteners - Taipei, Taiwan
March 25, 2008

A. Fe/zn 8 c5 :
means zinc coated iron with 8 micron thickness


Spec: Ep-Fe/Zn 8B free from Hexavalent Chromium (White)

Q. I have a print with this plate spec, and just want to make sure that I understand it correctly. As far as I know it is a .00031 min plate thickness, ROHS.

Is there a specific salt spray for this?

Any words of advise would be appreciated.

Amy Kolodziej
plate shop internal - Wyandotte, Michigan, USA
May 20, 2009

A. Hi Amy,
Yes the thickness is 0.00031 inch. This spec means white rust should not appear in 48H, and red rust in 96H more (total 144H).

Joko Prasetyo Yuniartanto
- Bekasi, West Java, Indonesia

A. We follow the detail FEZN8B.
Components require salt spray life up to 240 hours as per drawing of Honda components.

A.S. Kalsi
metal finisher - Gurgaon, Haryana, India

thumbs up sign  Hi Amy,
That is not a spec, it is a code within an unspecified specification number.

Joko and A.S.'s contradictory answers should serve as a warning not to proceed without knowing what spec number you are supposed to be following :-)


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

What is EP-FE/ZN10 BK Plating?

Q. Hello,

We have a customer from Japan that requires plating I have never heard. They are specifying Ep-Fe/Zn10 bk. I have contacted our plating shop and they have never heard of this type. It seems it is Zinc plating 10 microns thick, but what does the bk stand for? Please help.

Russ Kinyon
OEM supplier - Hutto, Texas
July 27, 2009

A. bk = black

GR Johnson
- Taiwan
November 2, 2022

Q. What is the meaning in the electrolytic coating spec "Fe/Zn8/F1" Pc:black passivation Cr+3 Fe/Zn8/F1 - FTR 00025 for an electrolytic coating of zinc on steel, with a minimal thickness of 8µ, is having a black layer of Chrome III passivation?

Ozgur Usluer
plating shop employee - Izmir, Turkiye
October 13, 2009

What type of plating is Ep-Fe/Zn 5/HB, CM2 C?

Q. We are quoting a job that has this requirement.

Renee Rider
Quality Manager - Columbus, Ohio, USA
April 12, 2011

What does "TLP" mean in spec Fe/Zn8/TLP?

Q. What is the TLP meaning in the electroplate spec Fe/Zn8/TLP

- Johor Bahru, Johor, Malaysia
June 24, 2012

A. Hi. Google tells me that TLP stands for 'thick layer passivated'.

SK Cheah
- Penang, Malaysia
June 26, 2012

Q. What is HB in 'Ep-Fe/Zn[2]/HB CM2'?

Yan Biau Chow
- Singapore
July 2, 2012

A. Hi.

HB indicates a post treatment of Baking for Hydrogen removal.

SK Cheah
- Penang/Malaysia

Q. What about CM(iii)3?

- Seremban, NS, Malaysia
April 16, 2013

Q. What does EP-Fe/Zn-Ni8/CM2C mean? Could you help me to understand this specification?

Armando Diaz
- Metepec, Mexico

thumbs down sign I remain a bit shocked by this thread, cousins. The specs say what their codes mean. Are people actually issuing certs based on internet rumors?

Bone joor :-)

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


Q. We have some steel fasteners in our older drawings with a description of "GRADE 5, 2C". Our internal part number corresponds to, for example, McMaster 90126A031. I assume that the 2C designation is meant to suggest the zinc-plated finish but I haven't been able to find a standard that it would be associated with. The only references I've found are ASTM A193 (appears to refer to a heat treat for SST) and BS1706, where it doesn't mean much without additional context. Our customer is now asking for clarification so I need to come up with an answer. Can anyone give me a hint? Thanks!

Mark Treadwell
engineer - Baltimore, Maryland
July 16, 2013

A. Hi Mark. My guess is that the fateners are stainless steel based on the spec you referenced, and that "2C" refers to the thread fit rather than having anything to do with zinc plating or chromating ... but this doesn't sound like a job to be guessed at, it sounds like a situation where a qualified engineer should study the drawing and issue an appropriate revision.
Luck & Regards,

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

What is SEZn-CM finishing?

Q. Hi, I'd like to find out what is SEZn-CM finishing. This is stated in my customer drawing under surface treatment so I'm checking what finishing is this.

Best regards

Ivan Teo
- Singapore
May 14, 2014

A. Hi Ivan,
If this is on your customer drawing your best bet is to ask your customer what it means.

Never ceases to amaze me, how were you ever able to quote for the job if you didn't understand what it entailed?

Brian Terry
Aerospace - Yeovil, Somerset, UK

Q. Hi Team,

Anybody able to advise me whether DIN 50691 Fe/Zn8b is equal to ASTM B633?

Sugumaran s/o Doraisamy
- penang malaysia
December 10, 2014

A. Hi Sugumaran. I am not able to find a "DIN 50691" spec. and suspect a typo, and that that you actually meant DIN 50961, superceded by DIN 50962 . That spec and ASTM B633 are different specs, so they are not "equal" -- but I believe it will be possible for your plating to comply with both of them. Good luck.


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

What is Ep-Fe/Zn8/C? Same as ISO 2081?

Q. I'm finding global specification callout comply with PFZn8-C. I'm not sure where this callout comes from. I guess it's the same with Fe/Zn8/CM2. Am I correct? Then can I use ISO callout ISO 2081 Fe/Zn8/C?

One more thing: Is there any expression which regulates trivalent passive chromate?
Sorry for many ugly questions ...

Seungsik Won
- Daejeon, Rep of Korea
August 28, 2015

Q. Hi team, please help!
What does "Cr 3" mean in "Ep-Fe/Zn 5/CM2 Cr 3"?
Thanks so much!

- Hanoi, Vietnam
January 7, 2016

What color is EP-Fe/Zn5 C3 plating?

Q. Hello,
I received a Salt Spray Corrosion Test Tracking. The treatment for the product is Ep-Fe/Zn5 C3 which I know coating thickness is over 5 µm. What coating requirement color should it be? It says "BLUE" but I thought it was green finish. Do they make a mistake or is that correct?
Thanks in advance!

Denisse De Leon
Supplier Quality Assurance - Reynosa, Mexico.
January 25, 2016

UNI ISO 2081

Q. I just received some parts with this specification UNI ISO 2081, Fe/Zn 12c 2C. I have copy of specification but I don't understand the 2 in front of the C. I understand that the C is or iridescent coating but I'm wondering if the 2 has something to do with trivalent/hexavalent type. Also the 12 I am assuming is for 12 micrometers, but what is the little c for?
Thanks in advanced for all the responses.

David Juarez
Electroplating Job Shop - Orange, California USA
June 21, 2016

Q. Hi, I work for a valve manufacturing company. One of our customers gave us a plating specification saying:
Surface protection "FeZn 8 Cr III Y SS:8451 S2"

Now, although I have been reading these threads and have found out that FeZn8 probably means Zinc plating with 8 microns thickness, I am not able to find Cr III anywhere. It probably means Chrome passivation but what does III mean.

Also, does SS 7451^8451 S2 mean salt spray test for moderate conditions (S2)?

Please help.

Mihir Bajekal
Triton Valves Ltd. - Mysore India
March 23, 2017

Q. Can you please advise what Honda Spec MIC Black is?

S Zuroweste
- St Louis, Missouri USA
October 18, 2017

Q. A question related to: electroplated coating Fe // Zn-Fe8 // Fn //T2

Fn means black - but what exactly does BLACK mean?

is the BLACK specified somehow?

Marek Kasprzak
- Czestochowa, Poland
December 4, 2017

A. Hi Marek!

That specification is explained in DIN 50962 .

Fe // Zn-Fe8 // Fn // T2
(Iron substrate // Zinc-Iron Layer, 8 microns // Black passivation // Sealed)

Black is specified as it is: Black passivation. There are many vendors of proprietary products to get this black color and achieve the required salt spray performance.

I suggest you to get this standard and read if this coating has any other requirements, or if your client has any expectation about this finish that is not in this spec.

Best of luck!

Daniel Montañés
TEL - N FERRARIS - Cañuelas, Buenos Aires, Argentina

Q. Have a print that calls for FE/ZN Cz plating Can you tell me what the Cz stands for?

Dennis Carter
Tube bending - Bay Port, Michigan USA
August 14, 2018

Q. We have inquiry for zinc plating electrodeposited coating ISO 2081 -Fe/Zn8/T4-trivalent clear passivate and torque and tension top coat TnT 15 to meet NSS hours of 120 hours white/384 Red corrosion. What does T4 mean? Thank you.

Dallas Sitinjak
- Batam, Indonesia
November 29, 2018

A. Hi Dallas,

It means "Application of grease, oil or other lubricants". There is a list from T1 to T5 of supplementary coatings over zinc in ISO 2081.

Best of luck!

Daniel Montañés
TEL - N FERRARIS - Cañuelas, Buenos Aires, Argentina

Q. Dear Sir May I know the breakdown of plating Fe/Zn 8-CB? Sometimes we receive the color always different. Any matrix color for this plating type? Thanks.

M Thohir
March 19, 2019

Q. We are quoting a electroplate spec and want to better understand the "breakdown" of the spec. Ep-Fe/Zn5/CM2C

Fe : substrate to be plated
Zn : kind of plating
5 : thickness (8 ^5 CM1 : blue chromate
CM2 : yellow chromate
C: ? Does anyone know what the C means?

Omar Mondragón
Electroplating - Cd. Juárez Chihauhua, Mex
June 13, 2019

A. Hi Omar. When we receive postings from other countries, we often must start by fixing symbols which come across wrong because of keyboards differences, letters that don't exist in English, accent marks, etc. Your name and town came across as: 35197-2.

On postings from some countries we must change " ı " to " I ", etc. Yet people quote abbreviations without saying what specification they are from, and ask what was meant. Spec writers don't swear an oath what their terms will mean. It's dangerous -- we have several threads where people misinterpreted what was intended by "Type 3" in regard to aluminum processing :-(

You say the "5" means "8 microns" -- it's possible, but says who? I think it 'ought' to mean 5 microns. Please tell us what specification you are referring to, then all can be revealed. Thanks!


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

Q. Sorry!

Is correct.
Spec ISO 2081 Ep-Fe/Zn5/CM2C

Fe : substrate to be plated
Zn : kind of plating
5 : thickness (5 mic)
CM1 : blue chromate
CM2 : yellow chromate
C: ? Does anyone know what the C means?

Omar Mondragón [returning]
Micro Procesos Industriales S.A de C.V - Juarez, Mex

Q. Looking for a breakdown of this finishing spec.:
STD3947, Fe/Zn-Fe8c4

Jeff Miller
- Gardena, California
February 5, 2021

Ed. note: Sorry, we are unfamiliar with any such spec as STD3947 and believe it may be a typo.

Please see letter 26629 for another long list of similar sounding Q&A's about plating specs.

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"