Zink Test

zinc

Put it in boiling water for less time, Mildred.

The surfaces are not really that similar, but there are a couple ways that might assist you in distinguishing.

Note the ease with which the surface layer can be scraped off.

Note how reactive any scraping you get are with sulfur (look in garden supply..and some heat needs to be applied to get things started).

Or, you could Note the number of related hospital admissions for metal fume fever from heating scraping with a torch in a poorly ventilated occupied room.

Zinc is easier to scrape, reacts with sulfur readily, and if you heat it and breathe the fumes is more likely to send you to the hospital; compared to mild steel.

Reverse the electroplating polarity.

GA for that.

Zinc and freshly milled Mild Steel may look similar at first glance, but steel oxidizes quickly, gaining a dull grey patina⁽¹⁾ within a day or two. Unless one is being given two freshly-milled cubes and being asked which is raw steel and which is zinc plated, the difference should be obvious.

And the texturing is a dead giveaway, especially if the steel has been 'dip coated' rather than electroplated, although the dip coating is used more for small items like screws instead of large things like bar stock⁽²⁾.

Notes:

1. I know 'patina' is usually used to refer to the green coating on copper, but it actually describes any oxidide or sulfide coating on metal or stone.
2. People don't REALLY zinc coat raw stock, do they? I always thought of zinc plating/dipping as something that is done as a last step to a finished product, after all the forming and machining is done.
   

2. How about pipes and tubes and unistrut and flat sheet...

Large and small items are regularly both either hotdip galvanised or zinc electroplated depending on their final use.

Then there are various zinc coating repair techniques.

So, yeah, you can normally tell by looking whether or not steel is zinc coated.....how thick it is, is another story.

I did not know that.

Thank you.

Put on rubber gloves and don't put your nose too close, i.e. don't snort the vapors like cocaine is snorted. Get a small covered jar such as an old peanut butter jar. Take a small sample of the zinc/steel, about the size of a tooth- pick and place the smallest quantity of the mercury on the metal sample, use a small eye dropper or pipette with a rubber bulb on the upper end (sometimes called a "pro-pipet" sp.?) Take a small amount of Hg, Mercury and place the metal/Hg sample in the jar. Add water till the sample is covered. Wait overnight. If it is zinc, the droplet will have been absorbed into the zinc and form an amalgam such as the old dental amalgams that were a mixture of silver, copper, mercury and zinc. It may also be s little shiny. Some of the older people remember making silver coins shiny by rubbing them with mercury, shiny at first but then dull in a few hours.

If it is steel, the material that the carboys that mercury is shipped in at 1 metric ton each, the mercury will still be on the surface of the sample or has fallen to the bottom of the jar with water in it.

Environmental and PPE--- Since you are using an extremely small quantity of Hg and it is open for a minute or less there is no detectable vapors for respiratory intake. Wear the rubber gloves as a precaution. If the eye dropper/pipette are used there will be no dermal contact. Water stops the Hg vapors from going into the air. Metallic Mercury/water processing separators work exactly this way. If you were to break a Hg thermometer your exposure to mercury vapors would be exponentially greater than this simple experiment.

Mercury forms an amalgam with zinc. If the sample was zinc ask your dentist how he disposes of dental amalgam, be nice and ask him if he would include this sample with his. If it was steel take a half a teaspoon of zinc powder and add it to the sample in water. Shake the mixture and let it stand overnight. Separate the resultant amalgam and powder from the water and talk to your dentist for disposal. The water no longer contains Hg so it can be diluted and placed down the drain. Rinse the container in the same way.

Ok, this seems like a long procedure but it isn't and it isn't dangerous. This is the way that Hg is removed from Hg/water solutions in stainless steel tanks. The mixture is agitated with zinc powder and the solids filtered from the water. The water is then disposed of in the sanitary sewer and the solids (55 gallon for each container) are sent for reprocessing by heating the solids to vaporize and condense the Hg.

During one part of my career I was an engineer at a plant that made Phenyl Mercuric Acetate for use as a biocide and preservative. This is how our state of the art waste water processing area operated. Same method as mentioned above as the test but much, much larger batches.

Of course there are much simpler and shorter methods with Mercury but I'm not going into that. This is the safest procedure, some of the others are not.

Good Luck, Old Salt

Unfortunately quite the opposite is true. Metallic mercury poisoning is a chronic problem. The mercury salts are an acute problem. When fish absorb mercury it is at a very low absorption rate and the poisoning is accumulative since it must be absorbed into the cells. Mercury salts on the other hand are readily absorbed by ingestion, respiratory, skin contact, and a few other means. For example, the mercury salt that was cited, Phenyl Mercuric Acetate (PMA), is extremely hazardous to the skin among other ways. The burns from PMA don't usually show up for between 2-24 hours. When they do appear they are extremely painful and usually of the 3rd degree type. They have red blisters and any movement of the skin or touching the blister is so painful that it must be treated by a doctor and especially one who knows what to do. The normal treatment is to initially debride the blister. This means the blister must be broken and the outer skin of the blister cut off and the burnt skin protected from infection until it completely heals. All this time the pain is very intense, just like a 3rd degree thermal burn would.

Fortunately there is one soap, ZEP F-7, that will wash this material off if used promptly (less than 1/2 hour) after exposure. There is also a meter, made by Jerome, which can readily detect mercury vapors.

Just by virtue of how it works as a biocide and other functions it is bad stuff. Anything that is made from all Hazardous Chemicals has very little chances of not being bad, mercury, benzene, glacial acetic acid, anhydrous ammonia and a few other magic potions. Extremely toxic. The probable oral lethal dose for humans is 5-50 mg/kg, between 7 drops and 1 teaspoonful for a 70 kg (150 lb.) person.

It had been manufactured in the USA but the EPA banned its use in 1990. The largest use of PMA was as a preservative in Latex Paint. Now most is manufactured in Spain.

The following literature is quite informative about this mercury salt:

https://www.fishersci.ca/viewmsds.do?catNo=AC417630250

http://nj.gov/health/eoh/rtkweb/documents/fs/1502.pdf

During my tenure where it was manufactured I often did the new employee Haz comm and Right-to-Know orientation. I strongly told everyone to was their hands frequently just in case they might touch it. I also emphasized that they should wash their hands carefully before going to the bath room. Yes, an employee would occasionally get these extremely painful burns on their crotches. Would you want a Dr. to debride you down there? It would be every painful, wouldn't it?

One production manager who had a very nasty attitude was the object of some of this material placed in his steel toed safety shoes. He put them on and yes his feet were severely burned. He couldn't walk for 3 weeks.

Yes, I am also a believer that some measures of handling Hg are not necessary. I do know though that this stuff is bad sh$t and forget my opinions and handle it with extreme care. It anyone ever got these burns, as I once got a small one, they would agree that mercury salts are extremely bad materials and treat them with all due respects.

Good Luck, Old Salt

Select another metal (e.g. nickel) from the electromotive series. Put both in a conductive electrolyte and measure the voltage between them with a voltmeter. The voltage should be the difference in the electromotive potential between the two metals from the following table:

You should see about a 0.32 volt difference between iron and zinc and the reference electrode. For example, if nickel is chosen as the reference, the difference is 0.19 volts for iron and 0.512 volts for zinc.

Quick test- get a can of powdered drain cleaner, dissolve a heaping tablespoon in one cup lukewarm water (NOT hot, as it could boil and spatter caustic solution all over). Wearing latex or similar gloves, wipe some of this on the metal in question.

As this should give a solution of around 10% sodium hydroxide, it will react with zinc and the natural zinc oxide coating to dissolve it, with generation of hydrogen that may appear as bubbles. It will not visibly react with carbon or mild steels, other than possibly speeding up the natural oxidation to iron hydroxide.

You could make a test system with a DVM on a low scale. With your lemon acid in water you will have a sort of battery when applying 2 different materials and nothing when the same material is submerged. This is only for small stuff.

On a flat surface acid may react immediately with the zinc and produce harmful smoke.

When new they look alike

Seriously? Never not seen the difference myself, pretty obvious really.

If visual identification is impossible, not my eyes they're the OP's, the uncoated steel, if not covered in oil, will have rusty marking pretty quickly with a wipe of vinegar or lemon juice or just from your finger prints.

Other suggestions proffered are good too.

Why do you need to know this Yuri?

Want to order some plates. Once ordered an elbow, it was shiny and looked plated when I took it but soon rusted.

So, I'm going to take along a small lemon and a knife.

Thank you all for your answers !

I agree with Wal. It is very easy to tell just by looking. I think you may be having difficulty telling the difference between zinc plated and hot dip galvanised. Non coated steel, if it is shiny like zinc coating, will rust overnight from the touch of your hand. I will add the rider that it must be clean and free from a preservative coating such as oil or lacquer.

Jim

I was going to say GOOGLE zinc but since you cannot spell it I guess you wouldnt get very many "GOOD" results if you GOOGLE zinK.

Top result from a GOOGLE search for ZINK!

Zink is the Germanic word for zinc......

Zink is the Germanic word for zinc......
I guess GOOGLE isn't Germanik.

Yah, everything but the kutchen sink!

Or you could dip the suspected galvanized metal (zinc coated) into some lemon juice with a copper wire also in the juice. A copper deposit will arrive on the zinc (due to the corrosion of copper in the lemon juice, and subsequent plating of the more noble metal on the zinc, which also serves as protective anode for the iron, and also will make this into a Daniell cell (a poor one). The zinc should not plate on the copper, so do not worry about that, zinc is an active metal with a tendency to be the anode.

A "destructive test" would be to stick some of it in a caustic soda solution. NaOH reacts vigorously with Zn to give sodium zincate and evolution of hydrogen gas. The hydrogen gas can be ignited if you like to give a little "pop."

2NaOH + Zn = Na₂ZnO_{2 +} H₂

_{Iron has no reaction with caustic soda. (oh dear it's gone whacko again)}

If you can stand the material loss, a touch with a grinder will remove all doubt. Plain carbon steel will show bright sparks, not the galvanized surface. This is how we made sure the zinc was removed from an area to be welded.