Where the
world gathers for metal finishing
Q&As since 1989


-----

Rusting of steel pickling tanks

Dear sir,

We are using HCl for Acid pickling in tanks. After acid pickling we use to wash the tank with water. Even though after 3 hrs the rust forms.To neutralize the acidity, please suggest some chemicals, also to prevent further rusting what chemical should we apply.

DAMODAR
automotive - FARIDABAD, Haryana, INDIA
2003

---

I may be misunderstanding you. It seems unbelievable that you could be using steel tanks for pickling, Damodar.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

---

2003

Hi Damodar!

Ted's reply was right on! I said to myself, Holy Cow, who in the heck suggested m.s. tanks for HCl ? You won't find an 'additive' to solve your problem. Nothing! You have a few options
l. Use a loose liner made of PVC
2. Bond, ie. glue-on a flexible PVC lining material
3. Paint the inside using a suitable resin
4. Better still, apply a coating of fibreglass to the tanks

For # 2, you'd need an expert to do this correctly.
For # 3 you'd have to sandblast the tank first of all.
For # 4, again sandblast and then use some fibreglass matt AND a suitable acid resistant resin ... but this work should be performed by someone who knows what they are doing.

The disadvantage of # 3 is that a painted coat could get easily scratched and therefore become useless. You didn't give any indication of the size of the tanks nor the operating temperature ...'tis easier to come up with a possible solution if all facts are given.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

I agree with Ted and Freeman. It is dangerous to use steel as HCl is quite aggressive acid. I guess, you might have to use two tanks (an outer stainless steel - only as an containment in the case of accidents) and a plastic tank to hold the acid. You might have to find more details such as what kind of tank would be more suitable for your conc. of acid. Again go for seamless tanks (rotomolded). Contact sintex, Kalol, Gujarat (India) they might suggest you with the correct plastic tank or Central Institute of plastics Engineering and Technology (CIPET) for more information.

M A Balachander
Bristol Aerospace - Winnipeg, Canada
2003