Passivating SS Pipe

A. Contact time for the passivation solution should be hours, not days, but if there's a lot of piping, several days of site work could be involved. I'm not familiar with the valves you mention, but if they cannot withstand any passivation solution (including citric acid, the mildest), the usual practice is to remove them, install SS spools in their place during passivation while they are cleaned by some other method. This sort of work is done routinely, and the firm which is doing the passivation should know how to deal with it.

A. This can easily and safely be done with proprietary citric acid formulations. Normal cycles for new equipment are a maximum of one hour, but it depends mostly on the cleaning, rinsing and drying cycles, which will bring the entire cycle up to a few hours at least.

If you need help, we can refer you to excellent contractors who can do this for you or give you directions on how to do it.

A. Frank,

I would simply refer you to ASTM Specification ASTM A967. In addition, ASTM ASTM A380 will provide some valuable guidelines. I will echo the previous responses and recommend that any process controls, sensitive valves, or other critical equipment be removed from the system before passivation. I will often have a customer ask "how long" the passivation process takes. While the chemical circulations may only require a few hours in total, prepping the system, circulation equipment setup, and dry time will add considerably to the overall schedule. Hope that helps.

A. Hi, Maricel. Joseph Lockrem answered your question. Please follow the links he offered and you will see these tests for whether the passivation is okay:

• 1.4.1 Practice A - Water Immersion Test,
• 1.4.2 Practice B - High Humidity Test,
• 1.4.3 Practice C - Salt Spray Test,
• 1.4.4 Practice D - copper sulphate ⇦ this on eBay or Amazon [affil links] Test,
• 1.4.5 Practice E - potassium_ferricyanide [affil links]-Nitric Acid Test, and
• 1.4.6 Practice F - Free Iron Test.

Good luck and Regards,

A. Hi Ashok. You just Google for a firm which offers "on-site passivation"; there are at least four or five well-known international firms as well as local services ... or were you looking for the name of a book? Good luck.

Regards,

A. Good luck getting a detailed answer to that, Ashok.

The people Who know the exact details of on site passivation have spent hundreds of hours and thousands of dollars learning the details and fine points.

They're not going to give you, gratis, that which they have invested in.

You can hire people who know to do it for you, or you can invest your own time and money to learn.

A. Ashok,
When passivating the outside of a pipe system, a paste or gel type passivation product is typically used.

When passivating the inside of a pipe system, mix up a passivation acid solution that meets one of the industry standards and flush it through the system using a time and temperature that meets or exceeds the standard.

Both methods followed by water rinsing and drying, of course.