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Copper Sulfate Test Method


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


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 simply desk top unit is less than $3K. Fischer Technology makes an excellent unit.

Karl Weyermann
- Lebanon, Kentucky, USA


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


Todd -

I would suggest a portable XRF.

Terry Tomt
- Auburn, Washington



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


Actually, 3 people did answer Todd's question, Jessie, and answered it well. They informed him that the spot test he had seen used in a different application will not work in the application he is envisioning.

You can distinguish cows from chickens by counting how many legs are on the animal, but you can't springboard off of that success and use the "leg counting" procedure to distinguish cows from horses. Similarly, you can use the plate out of copper to detect bare steel in cases where you are plating with a nobler metal, but not when the plating is zinc, because copper will plate out on both steel and zinc, telling you nothing at all. It's like trying to use a "leg counting" procedure to distinguish cows from horses.

The responders offered two approaches that will work (by the way, all three responders work in plating shops, not for suppliers of test instruments).

In your case, perhaps the copper sulphate test would work; we don't know because you haven't described what you want to do yet -- but it usually considered a "gross" test, and in most cases the ferroxyl spot test is considered better.

But the test solution should start with reagent grade copper sulphate, and be 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], will give your QA department a headache they don't need, and there is zero possibility that Todd's "Big Three" would accept the use of Root Killer.

There is an ASTM standard for the copper sulphate spot test, but I don't know the standard number off-hand, and it may depend on the particular combination of top coat metal and substrate. Good luck.

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


That ASTM standard would be ASTM A262-13 [link is 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


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

Robert Rdeleted
petrochemical - The Hague, The Netherlands


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 ASTN 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

The mixture can be found in ASTM A967 [link is 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

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

Does this copper solution embrittle high strength steel?

Jo Fortin
- Montreal

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