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Electroplating iron nails with copper and zinc

I have done an experiment where I have electroplated iron nails with zinc and copper and then corroded them. I measured the starting weight of the electroplated nails and then measured the final weight of the nails after I corroded them. They each gained 5 grams. Why have they gained weight and not lose weight as they have corroded? does this mean the plated layer had corroded away and began corroding the iron nail to form rust deposits? HELP NEEDED STRAIGHT AWAY PLEASE!
thank you!

Alice C.
student - Hobart, Tasmania, Australia
June 14, 2009

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Hi, Alice. You're sure you weighed the nails after electroplating? 5 grams per nail is a lot of weight. Have you double-checked this? Photos of the nails after corrosion would help. It doesn't sound right overall.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 14, 2009

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Because the zinc is still there and it has added anions like chloride or sulphate. Several corrosion products contain water of hydration which will add weight. Also many of the corrosion products will absorb (or is it adsorb) water from the air.
To get a better weight, you need to clean the nails with a cloth and water. You then need to dry them in an oven at about 100C. This will give you the weight loss that you are looking for because you have removed the corrosion products.

James Watts
- Navarre, Florida
June 17, 2009

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June 28, 2009

I agree with last answer,

to make it real to real and avoid wrong results it is recommended that before weighing, do heating up of the nails in an oven to avoid humidity to be weighed as well.

Regards,

Dominik Michalek
- Mexico City, Mexico