Phosphoric Acid for rust cleaning / inhibitor: Mixture and Procedure

[happy-diver]

Can you O2 clean steel

 

[flymolo]

Because 1) there is nothing organic that can oxidize in phosphoric acid, the steel itself is more likely to combust than phosphoric acid "residue" (hint there isn't any) and 2) if you go re-washing it after your acid wash...

you are that much more likely to just reflash rust the interior which kind of negates the whole point of the acid wash in the first place. So yes, I wash with simple green to remove any oils, swap to phosphoric acid, rinse and dry it. Its perfect that way

I’m trying to avoid going the tumbler route at home. I think I'm gonna give this method a try. You just slosh some cleaning solution around in the tank and then do the same with the phosphoric acid solution?

Thinking I would add some compound o rust inhibitor as a third step and leave the tanks inverted to dry.

Would you use the same process for aluminum tanks, minus the rust inhibitor?

 

[tmassey]

Maybe I'm wrong, then. But I can't see that doing an acid wash and then saying "good enough, fill 'er up with oxygen!" would be a good idea. Would you do that?

So, with no direct knowledge of what’s going on, you voluntarily make a strong statement saying that “The tank would Definitely Not be oxygen-clean after an acid-wash”? Why would you do *that*?

There is so much voodoo and superstition surrounding “oxygen clean“. And for me, that is the biggest problem. People have strong yet ignorant opinions, and state them as facts.

That’s also because people have so little understanding of the requirements and risks surrounding oxygen. And yet again, people don’t go through the effort to address this.

Honestly, nothing that we are doing in the world of scuba cleaning is truly “oxygen clean“. I have friends that do rocketry projects with liquid oxygen. Their oxygen cleaning procedures involve multiple steps with multiple chemicals, including highly purified deionized water. On the other hand, we chuck some simple green and tapwater at it, slap the tank and say “this ain’t going anywhere“.

Yet we don’t see scuba shops blowing up or divers immolating themselves. Why not? Because we’re dealing with gaseous oxygen, not LOX. While there are certainly elevated risks with gaseous oxygen that we need to address, it’s order of magnitudes lower than liquid oxygen. So, just because there is an “oxygen cleaning” process out there, doesn’t mean it’s the right process for a scuba context. Or a welding context. Or a rocketry context.

Reducing this process down to gut feeling, rules of thumb, tribal knowledge and fear is not productive.

And for the record, the important part of this process is the rinse. Whether your final step is phosphoric acid or detergent, the actual final step is the rinse. You need to rinse everything away in that final step. If there is rust, you will need phosphoric acid to remove the rust. If there is hydrocarbons, you will need detergent to remove the hydrocarbons. But whichever step you do last, you will need a rinse to remove all remaining residue.

You get to do your own research to determine which will be easier to thoroughly rinse away: phosphoric acid or detergent. I have my own thoughts and have made my own decision. You get to do the same for yourself!

 

[tmassey]

I’m trying to avoid going the tumbler route at home. I think I'm gonna give this method a try. You just slosh some cleaning solution around in the tank and then do the same with the phosphoric acid solution?

Thinking I would add some compound o rust inhibitor as a third step and leave the tanks inverted to dry.

Would you use the same process for aluminum tanks, minus the rust inhibitor?

OK, you picked a very bad time to write this reply: I’m still in a bad mood after writing the reply above!

First of all, this is for steel tanks only. None of this should be done for aluminum tanks.

Second of all, I wouldn’t characterize any of this as “slosh some cleaning solution around”. There is a lot more involved.

Third of all, the concept of “add some compound o (sic) rust inhibitor” sounds terrible. These are breathing air tanks. The idea of chucking random chemicals in there because of their industrial properties alone does not sound… appealing to me. And that doesn’t even address whether that random chemical is oxygen compatible or not. You didn’t mention oxygen cleanliness, but I’m adding this for completeness.

Fourth, using said random industrial chemicals because it might allow you to “leave the tanks inverted to dry” sounds like choosing a bad idea to allow yourself to be lazy. With my concern already heightened because of my second point above, this point merely reinforces that concern.

My suggestion: don’t even think about doing any of this. Honestly, it’s not that hard of a process to do. But it requires a couple of hours, a small amount of equipment, and most importantly, a desire to do it right. If you don’t have those things, don’t do it. Have it done by someone who does.

I fully admit that this is a reply to a post that has irritated me, after having made a reply to a post that has irritated me. So I acknowledge the harshness. But I’m leaving it.

I also acknowledge the irony that I am upset at someone for taking this too sloppily, after replying to someone who might have considered themselves as taking it more seriously. But in the end, my problem is ignorance: opinions with no basis stated as fact, or randomly changing the process with unknown chemicals out of laziness.

Don’t do that.

 

[flymolo]

OK, you picked a very bad time to write this reply: I’m still in a bad mood after writing the reply above!

First of all, this is for steel tanks only. None of this should be done for aluminum tanks.

Second of all, I wouldn’t characterize any of this as “slosh some cleaning solution around”. There is a lot more involved.

Third of all, the concept of “add some compound o (sic) rust inhibitor” sounds terrible. These are breathing air tanks. The idea of chucking random chemicals in there because of their industrial properties alone does not sound… appealing to me. And that doesn’t even address whether that random chemical is oxygen compatible or not. You didn’t mention oxygen cleanliness, but I’m adding this for completeness.

Fourth, using said random industrial chemicals because it might allow you to “leave the tanks inverted to dry” sounds like choosing a bad idea to allow yourself to be lazy. With my concern already heightened because of my second point above, this point merely reinforces that concern.

My suggestion: don’t even think about doing any of this. Honestly, it’s not that hard of a process to do. But it requires a couple of hours, a small amount of equipment, and most importantly, a desire to do it right. If you don’t have those things, don’t do it. Have it done by someone who will.

I fully admit that this is a reply to a post that has irritated me, after having made a reply to a post that has irritated me. So I acknowledge the harshness. but I’m leaving it.

I also acknowledge the irony that I am upset at someone for taking this too sloppily, after replying to someone who might have considered themselves as taking it more seriously. But in the end, my problem is ignorance: opinions with no basis stated as fact, or randomly changing the process with unknown chemicals out of laziness.

Don’t do that.

compound "o" is an oxygen safe rust inhibitor sold for use in scuba tanks. i've been using it in my tanks that i tumble vip and fill for about 5 years now

Compound O - Oxygen Safe Rust Inhibitor - Gallon

john@northeastscubasupply.com

northeastscubasupply.com

would you have been less offended if i said "fill the tanks with a precise amount of solution and then roll them around on the floor with your foot?"

 

[tmassey]

compound "o" is an oxygen safe rust inhibitor sold for use in scuba tanks. i've been using it in my tanks that i tumble vip and fill for about 5 years now

Thank you for the clarification. Sidenote: capitalization exists for a reason. At least then I would’ve known to look for a specific chemical instead of suspecting a typo.

would you have been less offended if i said "fill the tanks with a precise amount of solution and then roll them around on the floor with your foot?"

Yes. Marginally.

Your entire post screamed vague and lazy corner-cutting to me. Your reply makes it a little less vague, but just swaps it with confirmation bias.

So to answer your original question with your additional detail: the procedure you outline does not match the procedure I have tested. You will have to decide for yourself if your process will work for you. It is not a procedure I personally would be interested in trying.

 

[flymolo]

Thank you for the clarification. Sidenote: capitalization exists for a reason. At least then I would’ve known to look for a specific chemical instead of suspecting a typo.



Yes. Marginally.

Your entire post screamed vague and lazy corner-cutting to me. Your reply makes it a little less vague, but just swaps it with confirmation bias.

So to answer your original question with your additional detail: the procedure you outline does not match the procedure I have tested. You will have to decide for yourself if your process will work for you. It is not a procedure I personally would be interested in trying.

Yeah, sorry. I didn’t mean to come off as flippant. I was just trying to briefly summarize the process in simple terms.

I like the idea of using hot water to rinse the tanks, I’ve just always rinsed with cold water followed by compound “o” before putting the tanks on a dryer.

 

[tmassey]

Yeah, sorry. I didn’t mean to come off as flippant. I was just trying to briefly summarize the process in simple terms.

(I hate the way this forum mangles YouTube links: the part starts at 1:58 and goes for 8 seconds. Here’s the link that starts there.)


For those who couldn’t be bothered to fast-forward:

Spoiler

Danny Ocean: And we’re going to rob it.

Linus: Smash and grab job, huh?

Rusty: Slightly more complicated than that.

Linus: Oh… Yeah!

Like I said, it doesn’t help that I was already irritated. But also: you can simplify something, or you can ridiculously oversimplify something.

With the amplifications to your original post, it sounds like you have a solid handle on what you want to do. I would suggest you try it out and see if it works for you.

For me, the rinsing and drying of the tanks are the most vital part of this entire operation. Again for me, it’s worth the effort to do it as rapidly and effectively as possible. Personally, I have found that if I do that, there’s no need for additional chemicals: O2 safe, breathing safe or otherwise. So I avoid them, because for me they don’t bring additional value.

It also doesn’t hurt that I eliminate a somewhat expensive chemical as well!

In the end, phosphoric acid is used for its rust inhibition properties. With a proper drying process, I don’t see the need for additional inhibition.

And that’s why none of this is necessary for aluminum tanks: they don’t contain iron. And therefore they don’t need rust inhibition!

OK, my blood pressure is down. If you do move forward this process, I’m certain others will be interested in hearing your results.

 

[rjack321]

Yeah, sorry. I didn’t mean to come off as flippant. I was just trying to briefly summarize the process in simple terms.

I like the idea of using hot water to rinse the tanks, I’ve just always rinsed with cold water followed by compound “o” before putting the tanks on a dryer.

This might be partly why you need a rust inhibitor in the first place. You want to be rinsing with the tank inverted and with the hottest water you have (120+F/45C) until the tank itself is downright warm and the water is residue free. Then blow dry with compressed gas (scuba air is fine). The warm tank and warm (residual) moisture with very dry air will facilitate evaporation and minimize flash rust.

Oxyhacker laid this out decades ago.

 

[stretchthepenn]

So, with no direct knowledge of what’s going on, you voluntarily make a strong statement saying that “The tank would Definitely Not be oxygen-clean after an acid-wash”? Why would you do *that*?

Because, according to my training in O2-cleaning tanks, the oxygen-cleaning process was supposed to be the very last step.

But, it appears that, according to people who know about such things or at least seem to, it's OK to reverse the process by doing a hydrocarbon-removal first and then doing an acid-wash. I learned something.

Chill, bro.