Descaling and Passivation on A 516 Steel

It's carbon steel, You can descale mechanically (shotblaster), or by acid pickling.

No passivation- Its not stainless; You can try a black oxide coating (it will be best when used in conjunction with oil film applied); you can try paint- Powder coatings are popular today, I'd personally choose oil base marine paint used for ships; you can try electroplating; you can also try a phosphate conversion coating.

But its carbon steel, it will rust given time and normal environmental conditions just about anywhere on the planet.

milo

You are right, Milo.

To protect the carbon steel surfaces, it is recommended to shot/grit blast in accordance with SSPC-SP 10, Sa 2-1/2 or SSPC-SP 5, Sa 3, then primed with zinc ethyl silicate, followed by the proper intermediate and top coats.

Abdel & Milo: Thanks you guys.

I am so sorry, because I wrote an incompleted information, We frabricated a REAL BIG SCRUBBER AND , HAS A BIG CHAMBER WHERE THE COOLING WATER RUNS, THE VOLUME IN THIS CHAMBER IS ABOUT 30,000 LITERS, ALL THE STEEL ON THIS IS A516 G70. So we are trying to descalate and passivate, I got formula on HCL 10-14%, after this RINSE til the water is on PH=7, and inject H3PO4 1-3%and rinse to passivate it is real, Do you know some NORM ASTM,ANSI REFERENCE TO DO IT CORRECTLY?

Thanks

Israel Barron

ibarron@sfmex.com

Try these. I'm not convinced the ASTM A516 materials are proper for this application.

http://www.chemetalloakite.com/products/by_app/phosphateCoatingsIron.aspx

http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA212240

background: http://en.wikipedia.org/wiki/Phosphating

milo

Israel,

what are you going to put in this tank when you have it completed (cooling water)? You might want to look at some kind of heavy coating that will either protect it from the contents or protect the contents from it. Then of course the coating cannot contaminate the water your cooling (if I read that correctly). There are many urethane and epoxy coatings that might work very well. I will check my ansi references when I get home this afternoon. Its been several years since I've worked with chemical processing tanks.

Scott

Scott

My customer is requiring a DEOXIDATION GRADE 2.212 , but I havent found nothing about this spec, I dont know if it is ANSI, ASTM,NACE, ETC...

My plan is to descale with HCL 8-14%,neutralize-rinse,H3PO4 3-4%,RINSE-stop.

According with your experience it is correct?

Israel Barron

ibarron@sfmex.com

www.promsa-mva.com

Israel,

I was way too busy when I got home to check specs when I got home yesterday. I have 3 1/2 year old twins. This will definitely get you etched down to clean metal and neutralize the HCL etch. There is nothing there to protect the metal after it has been cleaned.

I will try again today to search my specs for you.

Scott

Scott

I aprecciate your help buddy, Scott but if we put some H3SO4?

Thanks

Israel Barron

ibarron@sfmex.com

www.promsa-mva.com

it would be H2SO4.

Acid would remove scale. Would not "passify' this grade.

This grade is "intended primarily for service in welded pressure vessels where improved notch toughness is important." ASTM A 516.

I'm now wondering if you would need to bake out or artiucifcially age the steels after such an acid treatment in order to minimize potential hydrogen embrittlement?

NDT Tom, where are You?

After such an acid treatment, even if neutralized:

This steel will rust. This steel will rust. This steel will rust.

Speed of rust depends on temperature, species of ions, and available oxygen.

milo

Milo

My customer is asking for DEOXIDATION GRADE 2.212, I agree with you that it does not passivate, but it can be phosphating,it is not?

Israel Barron

ibarron@sfmex.com

www.promsa-mva.com

Deoxidation grade 2.212 might as well be santa claus. It is meaningless without the reference to the source document.

Just spraying phosphoric acid around is no guarantee of "phosphate coating."

Commercial phosphate lines for wire drawers typically used a Zinc Phosphate process.

Dip and dunk- ie in tanks.

Acid pickle. (good cleaniing is always the key)

COld water spray rinse

Hot water imersion rinse(150 or higher)

Phosphate coating (160-190 F) (More than 5 degree temp. variance results in coating uniformity issues)

Cold water immersion rinse

Neutralize rinse borax and lime Otherwise thin film of oxides of iron will form on surface.hot as possible.

Bake (225-300F)

Guys with hoses and mops- Not likely to be successful.

milo

I can't say it better than Milo did. I find no reference to "deoxidation grade 2.212"

I see big rust problems in your future.

Ask your customer for a copy of the specification he wants.

Scooter

Hi

Guys I was digging on the drawing and I found this "ENTROSTET NACH ENTROSTUNGRAD 2.212" I dont know if You speak german, but my original drawing shows me may be the drawing was designed 39 years ago. by DEMAG GERMANY.

Israel Barron

ibarron@sfmex.com

entrosten is verb for "to derust, to descale"

Entrostungrad I translate as "Derusting compound 2.212"

I'll bet its a tradename in Germany.

Gotta catch a plane.

milo

so, have you been able to go forward with your project?

Scooter

Scott

Thanks for your support.

We will perform the DEOXIDATION GRADE 2.212 with HCL 10-14%, with a pump and filter to recirculate, after this we will rinse with water til to reach PH=7.

I would like to heard your opinion about this?

Israel Barron

ibarron@sfmex.com

Israel,

this will leave you with a very clean surface. It will be very prone to rust unless your process will protect it or if you follow it up with some kind of protective coating.

It has been some time since I did this but I don't think there will be any protection from having a ph=7 when you are done. Someone who is more current can probably tell you for certain.

I wish you well,

Scott