Outdoor Weld Table vs Rust?

[ken572]

I would passivate in 100% nitric acid

Glenn,
Don't look so shocked. :

That was the perscribed procedure to do for (316SS) and (304SS)
so our welded area's would not get pin holes eaten in them from
our other solutions that would be put in them or on them.

Per our R&D Lab.

Back in the day - MEMORIES

Ken.

[Harold_V]

The mention of 100% nitric is likely not understood by the masses (that would have included me, had I not refined precious metals).

I am under the impression that what was suggested is that the nitric was simply not diluted, but used as it comes from the container. Typical concentration of tech grade nitric (most likely what was used by Ken's employer) is 68%. It is commonly supplied in 300 series stainless containers, and has no affect on stainless (aside from passivating).

Harold

[GlennW]

The Nitric I used came in a 2 pound glass ring necked jug. It had what appeared to be a black plastic screw on cap. I kept the jug on a beige Formica topped table, tightly capped, and over time the fumes that escaped around the cap seal fell down the side of the jug, ate the Formica, burned it black, and blistered it for about 12" around the jug.

That's why I was a bit surprised at the statement of working with 100% Nitric, when from what I understand, Passivating is usually done with diluted Nitric.

I also worked a bit with 98% Hydrogen Peroxide, and I'm not real sure which one was more fun...

[Harold_V]

The Nitric I used came in a 2 pound glass ring necked jug. It had what appeared to be a black plastic screw on cap. I kept the jug on a beige Formica topped table, tightly capped, and over time the fumes that escaped around the cap seal fell down the side of the jug, ate the Formica, burned it black, and blistered it for about 12" around the jug.

I'm not the least bit surprised, as nitric is a strong oxidizer (HNO3), which is the chief reason it is no longer sold to the common man.

That's why I was a bit surprised at the statement of working with 100% Nitric, when from what I understand, Passivating is usually done with diluted Nitric.

A reasonable reaction for those who are familiar with working to government specs. The addition of sodium dichromate assures the proper result when passivating, thus it is a part of the spec.

I also worked a bit with 98% Hydrogen Peroxide, and I'm not real sure which one was more fun...

I'd have to assume a neutral stance where that's concerned, considering I have no experience, but I get your point. H2O2 is also very aggressive and a strong oxidizer.

Harold

[ken572]

The mention of 100% nitric is likely not understood by the masses (that would have included me, had I not refined precious metals).

I am under the impression that what was suggested is that the nitric was simply not diluted, but used as it comes from the container. Typical concentration of tech grade nitric (most likely what was used by Ken's employer) is 68%. It is commonly supplied in 300 series stainless containers, and has no affect on stainless (aside from passivating).

Harold

Harold,
I thought I was loosing my mind, but I wasn't.

Nitric Acid Grade's.doc

(24 KiB) Downloaded 295 times

Please see attached.

Ken.

[Harold_V]

I'm amazed they'd use that grade, and it comes as a surprise that they did, but it's hard to argue with facts.

I used to buy my tech grade (68%) in a 55 gallon drum, one of which I owned. A simple exchange at the chemical store and I was good to go. At that time, I was paying right at $4/gallon.

Tech grade was more than adequate for refining, even silver. Even traces of chlorides in silver nitrate aren't good, yet one could dissolve pure silver with tech grade and distilled water with perfect results (necessary evil, as silver nitrate is the electrolyte for a silver parting cell). Concentration was reduced, but the acid was very white (clear) and free of troublesome contaminants. Makes me wonder why they used such a high level of purity, as cost goes through the ceiling. I learned that when buying reagent grade nitric for making test solutions.

As there was no mention of using sodium dichromate in your comments, I wonder if, maybe, that was their way of avoiding disposal problems. Chromates have become a real white elephant, even for disposal of solids. Any comments?

Harold

[ken572]

I'm amazed they'd use that grade, and it comes as a surprise that they did, but it's hard to argue with facts.

I used to buy my tech grade (68%) in a 55 gallon drum, one of which I owned. A simple exchange at the chemical store and I was good to go. At that time, I was paying right at $4/gallon.

Tech grade was more than adequate for refining, even silver. Even traces of chlorides in silver nitrate aren't good, yet one could dissolve pure silver with tech grade and distilled water with perfect results (necessary evil, as silver nitrate is the electrolyte for a silver parting cell). Concentration was reduced, but the acid was very white (clear) and free of troublesome contaminants. Makes me wonder why they used such a high level of purity, as cost goes through the ceiling. I learned that when buying reagent grade nitric for making test solutions.

As there was no mention of using sodium dichromate in your comments, I wonder if, maybe, that was their way of avoiding disposal problems. Chromates have become a real white elephant, even for disposal of solids. Any comments?

Harold

Harold,
We made all of our own products, and our company purchased top
grade everything, this way no one could mix low grade anything in
with the good. The passivation went very fast (15 minutes) with
solution at room temperature. We all had our own full head gear with
full face mask's that we washed, rinsed, dried, and installed new filter's,
and put back in a new air and water tight storage bag at our work bench.
We had and used one time chemical gloves and chemical suits that we
would cut up when done, so no one could reuse, and then put in to proper
disposal barrels and fill out the paper work on each barrel. If we had to
work in our hi-bred Chromic acid area's we would even cut our new chemical
boots uo in the bandsaw after we washed, rinced, and dried them. then we
would dispose of them in there proper barrel and do the paper work.

In regard's to your chromate question. Easy answer, and a long story short.

The City chemists would pull their little white van up to each of the two
man hole covers we had in front of our plant and take water samples
twice a day un anounced and test them. All chemicals and water were
deverted to the center of our plant where it was tested, treated, and
broken down chemicaly and made safe. All water remaining was drinkable.
All the bad sludge was pressed in our sludge presses and put into the
apropreate drums and sealed. Paper work filled out and off to the EPA
aproved burial ground. All of our ingredients for the products that we
made had a paper trail from our suppliers into us and through and with
our products to our customers, and when they were done with the product,
we would pay to have it shipped back to us for break down and disposal.
Oh and the paper trail would never stop until the products were cleaned
safe, and buried with the paper work at the EPA approved site. All toxic
fumes from our air tight production equiptment went out to a large after-
burner on the roof and was burn off at 1600 degrees to zero toxins. The
Chemists would climb up the stack and take readings every 30 minutes
and do their paper work. Lots of Paper Work. All Plant air in was fresh,
filtered, humidity, and temperature controlled makeup air. All plant air
going out of this plant was pulled through 20' high scrubbers with D.I.
water spraying down through poly ethylene media. All the run off scrubber
water went to the center of the plant and got treated before it left the plant.
Well I hope I didn't bore anyone. please excuse any and spelling error's and
or letter form etc.

Thank You for bringing back memories. This was a GREAT PLACE to work.
Ken.

[Harold_V]

Thanks, Ken. The process reminds me a great deal of the system that was installed at the facility I used to use for all finishing, Quality Plating, in Salt Lake City, Utah. As requirements were tightened, they were required to neutralize their discharge water and remove hazardous substances, then a filter press was used to remove them as solids, which were sent for proper disposal. They performed all manner of plating and finishing (no painting), including hard chrome and cadmium.

In a sense, the Salt Lake Valley was unique in that all discharge water ended up in the Great Salt Lake. There was no down stream use of the water.

The Great Salt Lake is virtually barren of life forms, aside from some brine shrimp and a type of small fly. In spite of that, they were still required to clean up their discharged water. Interesting, considering the lake is mined.

Yep, this entire matter brings back fond memories. My experiences go back no less than 30 years, and many of them much more. I hadn't thought much of this in a long time.

Harold

[ken572]

Thanks, Ken. The process reminds me a great deal of the system that was installed at the facility I used to use for all finishing, Quality Plating, in Salt Lake City, Utah. As requirements were tightened, they were required to neutralize their discharge water and remove hazardous substances, then a filter press was used to remove them as solids, which were sent for proper disposal. They performed all manner of plating and finishing (no painting), including hard chrome and cadmium.

In a sense, the Salt Lake Valley was unique in that all discharge water ended up in the Great Salt Lake. There was no down stream use of the water.

The Great Salt Lake is virtually barren of life forms, aside from some brine shrimp and a type of small fly. In spite of that, they were still required to clean up their discharged water. Interesting, considering the lake is mined.

Yep, this entire matter brings back fond memories. My experiences go back no less than 30 years, and many of them much more. I hadn't thought much of this in a long time.

Harold

Harold,
It's nice to think back and revisit lifes memories of our past.
We find that even the ruff times in life were great times.
I have been blessed with working at great company's and for
fantastic, and very smart and respectful people, my entire life.
I couldn't ask for more then that. It was all GREAT

Ken.