Corrosion Disaster - HCL + ZN vapors on home brewery.

Just a post of caution, not that this is likely to happen to the average homebrewer...

Last year I had a wood shed built which holds my brewing and woodworking equipment.
The last week of December I needed to remove what was either a zinc or galvanized coating from 4 small brackets so they could be welded and painted. Used a quart of muratic acid (30% hydrochloric acid) in a plastic shoebox.
To prevent animals from getting close to the toxic mix I put the mix in the shed and closed the door. I waited 18 hours for the acid to strip the coating off and it worked great! Very clean steel. Rinsed, washed and it was ready to work - nice clean steel.

Oh, the disaster part?

Two weeks later I went to get something out of the shed and noticed small evenly spaced black dots on my brewery. It appeared to be an oil. I was in a hurry and figured it was stainless and would simply wash off. I couldn't guess what it was.
Two more weeks go by and I wipe across one of the kettles to see what it is and notice some rust. Damn... this is bad, really bad.

Note electrical connection corrosion above.
Below -that thermometer isn't a cheap import...


This piece was made from certified 316L originally destined for a semiconductor factory which was scrapped because it wasn't shipped to clean room spec's from what I was told. I bought the lot for less than a dime on the dollar. Maybe you bought a racking cane from a homebrew store in Austin a decade ago? Nice stuff, electropolished interior. Overkill, but this demonstrates how nasty the fumes were.



This is a stick of 1/2" aluminum bar stock. Note "growth" on surface.
Tools, not showing them. The table surfaces aren't exactly smooth. Blades rusted. I don't want to look at the routers or wonder about the motor interiors.


This is about 1/2 of the stainless removed for cleaning.


Scrubbing with various grades of scotchbrite pads and bar-keeper's friend after thoroughly washing with soap, baking soda.

I was only able to do half a kettle before giving up.
It cleaned up fair. I would say 70%. The corrosion is by no means "gone"... and I haven't even touched the interiors. I may see if a pro-brewer can get a passivating solution, but this isn't going to be just a simple chemical bath to clean up.

This isn't the kind of investment I can just write off and not sure I want to call the insurance company and try to explain my "off label" use of pool chemicals.

Of course all of the nails in the shed are rusted. Not sure how I will treat them. Wire brush then either oil or rust-olium? Spray interior ceiling with rubberized coating?

Copper stuff has some damage but I don't think it will be ruined.

The only thing that doesn't "appear" to be damaged are enamel and powder coated surfaces. I haven't thought to check the carboys. The few damn things I have with the finish I hate so much - galvanized... appears to be fine.

Suggestions?

No suggestions for cleaning, but a warning with muriatic acid. Do not store it anywhere near things you don't want to corrode. Even in a closed container. It has the ability to out-gas even through it's plastic container and will just give you this nightmare again. I have a bottle of it that I used to remove aluminum from engine cylinders, and I leave that bottle outside for a reason. Stuff is useful but nasty.

I just finished a design for the $600k replacement of a ferrous chloride storage and injection system for one of my wastewater clients. Ferrous chloride is spent steel pickling liquor that once was pure hydrochloric acid. As the OP found, this acid does off gas. Hydrogen chloride gas evolves directly from the liquor into the atmosphere and it will permeate the typical HDPE jug too. The gas combines with atmospheric water vapor and becomes hydrochloric acid aerosol. Both the aerosol and gas are incredibly corrosive to almost all metals...including all grades of stainless steel.

As mentioned above, store that stuff outside and away from anything you want to keep.

PS: I don't think that the zinc had anything to do with your problem.

Also be aware that HCL and zinc create hydrogen gas which is very flammable. In an enclosed area, a spark, boom.

I don't store the acid indoors. Maybe if the Zinc or galvanized(?) coating had an effect it was that it made the hydrochloric acid fume excessively, (to release HCL vapor) sort of to a boil. Under the coating was steel.
There was also a "cold" front moving in as I was doing this so the temperature dropped 40 degrees that evening. I wonder if that made condensation an issue, I wouldn't expect it but no other explanation.
If I had an explosion, at least that's something I would have called the insurance company about! Kidding, I know that would have been bad.
I'll scrap some of the stuff, will work on the kettles at some point and fortunately have another set of keg-kettles in off-site storage.
I can't remember the product line of 5 Star, but the have a couple of with phosphoric and nitric acid for passivating. Before that, I still have to get through the etching.
I'm dealing with curved objects, and interior curves. I'll start talking to brewery owners who I've worked with in the past and maybe a couple of fab shops but already know they would tell me to scrap it all.
At the very least I'm out $150 mainly in abrasives, a small part of that in chemicals - if I go through with attempting to clean the kettles and three days labor. Replacing everything is wasteful, but the cost isn't that far off especially when I don't even know if it will work.
I built the brewery to work with either 60 or 100 quart kettles so part of me wants to upgrade.
So, anyone want a job sanding?

You said you left some things soaking in it. and left that container in the closed shed. that's all you need. I've read horror stories from machine shops where someone left a container of muriatic acid open in the shop and ruined tools and stock because of it. It's not something to ever leave in a confined space with other metal. That's just how that stuff is. Don't store it inside near anything valuable that you care about, even in a closed container.

That's GD tragic. Sorry for your losses

Bummer. I made the mistake, once, of storing bags of pool shock in my small shed over a winter. Had a brand new band saw in there waiting for me to make room for it in my garage shop. Bad deal. The motor came through unaffected.