52089

Passivation tank made of 304SS failed in a week  

April 29, 2009

We have a new stainless steel tank (304). We used this tank to passivate stainless steel parts. The composition of stainless steel passivation solution is 30% by volume Nitric acid and 2-3 Lbs./ gal. sodium bichromate. After processing 1 week, tank starts to leak.

Please help.

Vijay Kansupada
Regulator - Columbia, SC, USA

Vijay,

A very important question: Where did the tank begin to leak from? A weld? A fitting? A new hole that appeared?

Gene Packman
- Great Neck, NY

I'll bet it failed right adjacent to the welds. Carbide precipitation in the grain boundaries. Next time use 304L, or better yet, a lined tank.

Jeffrey Holmes, CEF - Spartanburg, SC, USA

Hello,
SS Tank is costlier.A cheaper and a better alternative is a high density PP Tank(Thickness of PP depends on the volume of the tank)or a MS Tank lined with a 10mm PVC or PP lining.

Subramanian Ramajayam     plating chemist Bangalore, Karnataka, India

Hello Vijay,

316L is a better choice.
Check for proper grounding.

Good Luck,
Micheline Forth

Micheline Forth
- Rincon, Ga, USA

I have used rotational molded medium density polyethylene tanks that were supported with either stainless beams for large tanks and enameled wood for smaller tanks with great luck. They cost less and are less likely to fail especially if the welder was poor.

James Watts
- FL

Hi Vijay,

The suggestions by others to use moulded hdpe tanks makes eminent success.

No,but no welding of the Pe tanks ... use tank adaptors ...
otherwise due to the nitric you'll get stress cracking at the weld areas.

Cheers from White Rock Freeman N.

Freeman Newton - White Rock, B.C. Canada