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Copper Sulfate Test Method to Verify Zinc Plating?


Q. My company produces car springs and stabilizer bars, approximately 1 million a month. I have been assigned a project to "Verify Zinc Deposition" on our parts. So I am seeking a method to visually see surface coverage of zinc on our parts. I have heard of a test using Copper Sulfate and submersing the parts in this solution for x time and upon retrieval from the solution the Copper Sulfate shows true zinc coverage. I have searched the web seeking an article on this method but cannot seem to find one. Can you offer any web site suggestions or describe this test method more for me so I may try it. We obviously produce components for the Big Three and would like to incorporate a test method in order to give them a warm fuzzy feeling that our zinc plating line is as good as we say it is. I have an SEM in house but would like a more simple test method for our floor operators to preform, as well the SEM can only look at a small portion of the spring I am looking for the entire surface.


Todd Sdeleted
- Florence, Kentucky


A. Why don't you consider a magnetic thickness tester. It is a nondestructive test and you can check the plating thickness any place you can place a probe. A simple desk top unit is less than $3K. Fischer Technology makes an excellent unit.

Karl Weyermann
- Lebanon, Kentucky, USA


A. The copper sulfate test in not unique to zinc. The copper simply replaces / exchanges for a more reactive metal. XRF would give you a spectrum of the metals present.

Fred Mueller
- Southampton, Pennsylvania, USA


A. Todd -

I would suggest a portable XRF.

Terry Tomt
- Auburn, Washington

Copper sulphate spot test


!! Todd,

Sorry to see that no one answered your question. I am looking for the same information and have had no luck finding any written procedure. Just as you got, everyone seems to have some other idea (maybe relating to a product that they use or sell) but either don't know or aren't willing to say what I need to know. I will give you what little help that I can.

First thing, copper sulfate is very easy and inexpensive to get. It is the blue salt used to kill roots that grow in your plumbing. 32 oz for $6-$7 at Wal-Mart. I have read that you can get it for less, in larger amounts, from farm supply stores. I got the 32 oz one, and due to lack of information, will start to experiment with it soon. Warning this is potentially dangerous stuff. Use caution if you do use it; protective glovesamazoninfo, apronamazoninfo, and Eye Protectionamazoninfo along with good ventilation. My need is to test steel, so the test will be different as will the results. I am thinking that a chemistry textbook may be a source of information if all other avenues are dead ends.

Good luck.

Jessie Adeleted
- Waukegan, Illinois, USA


Hi Jessie. People did answer Todd's question of how to verify zinc deposition. Unfortunately, the copper sulphate spot test won't work in the situation he is in. While you can distinguish cows from chickens by counting how many legs are on each animal, you can't use that method to distinguish cows from horses because they both have four. Similarly, you can use the plate-out of copper to detect bare steel voids only when you are plating with a nobler metal, not when the plating is zinc ... because copper plates out on both steel and zinc, and tells you nothing.

Test solutions should start with reagent grade copper sulphate, made up exactly the same way every time. Using an undocumented concentration of possibly contaminated copper sulphate, intended for use as Root Killer [linked by editor to product info at Amazon], may give your QA department a headache they don't need; Todd's "Big Three" won't accept the use of Root Killer. There is an ASTM standard for the copper sulphate spot test. Good luck.

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


A. That ASTM standard would be ASTM A262-13 [link by ed. to spec at TechStreet] , copper-copper sulfate test designed primarily to test for ferrite formations in austenitic stainless steel. Enjoy!

Jeff Swayze
- Kelowna, B.C., Canada


A. We use Zinc tracer to detect Zinc contamination on stainless steels. 2/100% Dithizone + 10% NaOH in demineralized water. It turns pink if Zn is present.

Robert Rdeleted
petrochemical - The Hague, The Netherlands

Recipe for copper sulphate test solution


Q. Can anyone provide the recipe for copper sulphate solution? I found some crystals and someone told me to just mix it with water but weren't sure how much. I need a quick answer and would prefer to cut through the red tape and avoid purchasing the purchasing ASTM A262 test procedure one poster linked to this thread. I need to check some stainless steel mold parts for ferrous content now and also want to use it to determine the presence of chrome or lack thereof on injection blow mold tooling.

Ron Myers
plastics - Jackson, Tennessee USA

February 5, 2008

A. The mixture can be found in ASTM A967 [link by ed. to spec at TechStreet] Chemical Passivation for Stainless Steel Parts

4 gm copper sulfate pentahydrate CuSO4.5H20 (we use reagent grade)
250 ml of distilled water
1 ml sulfuric acid H2SO4 (specific gravity 1.84).

Solution is swabbed on part, let stand for 6 minutes minimum part should be carefully rinsed and dried ... if copper deposit is observed then free iron is on the surface of part.

Dennis Cope
- Ontario, California

February 14, 2008

A. I agree with Dennis Cope. I am looking at A967-05 and he has the exact formula and time of exposure. Dennis gets the prize for your question. I am looking at getting lab grade powder of Cupric Sulfate, 500 grams of powder for $15.96 and 90% Sulfuric Acid from in Austin,Texas. They supply mainly to schools.

You can buy copper Sulfate test solution through Stellar Solutions, the makers of Citrisurf. It is $10 for a two ounce bottle, ready made.Good Luck

Ken McElroy
medical - Austin, Texas

September 30, 2009

Q. Does this copper sulphate test solution embrittle high strength steel?

Jo Fortin
- Montreal

Difference between copper sulphate and copper sulphate pentahydrate

April 19, 2014

Q. Hi , actually 2 people did answer Todd's Question, Dennis & Ken and answer it well. They informed him that: 1. Dennis - Copper Sulphate Pentahydrate , 2. Ken - Cupric Sulfate.
... Till I got confused which one is correct among Copper Sulphate Pentahydrate or Cupric Sulfate or both to copper sulphate test solution. Suggest me.

Surya Narayana
Process Engineer - Tumkur , karnataka . INDIA.

April 2014

A. Hi Surya. Again, the copper sulphate method cannot be used to "Verify Zinc Deposition" as requested by Todd, but it can certainly be used for other purposes.

Copper Sulphate Pentahydrate or Cupric Sulphate Pentahydrate is the correct long-form of the chemical name. Cupric means copper in oxidation state "+2", which it always is when combined with sulphate, so it doesn't matter whether you say "copper" or "cupric". And "pentahydrate" means that this hydroscopic compound will absorb 5 parts of hydration water if you let it (if you don't seal it away from the air), forming the familiar blue crystals. Copper sulphate is just a short form which people understand to mean cupric sulphate pentahydrate. Good luck.


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