What Happened???

[TuckerMike]

I was out in my sugar shack last night, test firing my D&G 2x6 arch, looked in to the bottom of the finishing pan and could see several tiny pin holes all over the bottom of the pan and could see down in to the fire box. When I drained the pan and looked at the bottom it was wet all over (obviously), but the holes were so tiny they would only form a drip every few seconds. The flue pan also has 1 tiny hole up near the firebox, but that is all I have found so far.

I have no idea what happened. I bought this arch used and have only used it myself for 1 season. Can anyone help me out on the cause of this?

Thanks,Mike

[DrTimPerkins]

I assume this is a welded pan and the leaks are in the pan material itself (see attached photo below) and not in the welds or solder joints. Tell us more about how the pan was used and then stored last year? How did you clean it during and after the season (inside and bottom)? What fuel (or other things) are you using in the arch? What type of SS is it? Photos?

Pinhole corrosion is typically caused by oxidation (often associated with using chlorine or other strong oxidizers to soak/clean without adequate rinsing) or sometimes by carbon build-up on the bottom containing chlorine or other salt residues that get hydrated in storage. Not saying that is it, but it a common cause of these failures.

Unfortunately there is not much you can do to fix it if the corrosion is extensive. It'll get worse over time.

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[Walling's Maple Syrup]

Is it an oil fired rig?

[TuckerMike]

I don't have any pictures of it yet. Stainless pans, welded. holes are in the bottom of the pans. For storage I did a citric acid soak and then did a chlorine rinse to kill off any "bugs" after letting it sit all summer. I thought I effectively rinsed it each time...but maybe not?

It is an oil-fired rig.

[Walling's Maple Syrup]

Did you clean bottom(underside) of pans after the season last year?

[TuckerMike]

I did clean the bottoms of the pans, but no to shiny stainless. I brushed the heavy carbon off and hosed the majority of the remaining carbon off.

[Walling's Maple Syrup]

Is there any shiny ss showing on bottoms of pans? Do you use off road diesel? #2 fuel oil? Cut with kerosene? I believe it may be oxidation of fuel oil residue.....is your Burner tuned properly? You shouldn't get too much black on bottoms if it is

[TuckerMike]

Offroad diesel (ULSD). Nothing shiny on the pans. I've always struggled with carbon buildup, but my chimney has no smoke when operating. Figured it has to do with relatively cold metal due to sap on the inside. I'm headed out to clean them up and inspect the holes. I'll post some pics when I've got them clean.

[TuckerMike]

Apparently these pans aren't made of high-grade stainless? I thought a stainless pan would be less susceptible to chemical attack than this? I get that I need to keep the equipment clean, but I work in the power industry and we certainly don't worry much about carbon residue on stainless parts on boiler equipment. This is my first commercially built pan...so I'm still learning and appreciate the responses/input.

[Cjadamec]

It's not the carbon so much that you are concerned about. Its the sulfur oxides in the exhaust getting trapped in the soot that then turn to sulfuric acid when exposed to moisture in the air. The carbon holds the acid onto the pan. This is also known as "cold end corrosion". This tends to occur most when diesel fueled exhaust is "cold" which is around 300F. Although it still happens to a lesser degree at hotter temps. A poorly tuned burner which is evidenced but excessive amounts of carbon soot makes this problem worse as well. Carbon from a poorly burning burner will generally produce "fluffy" soot and tends to form soot balls. Soot from a tuned burner tends to be harder and more tar like.

If the pin holes in the bottom of the pan are small and shiny on the inside of the pan its more than likely your corrosion issue is coming from the fire side. The area around the pins holes in the fire side will likely look dull or rusty and have a dished out look and be much larger than the hole itself.

Stainless tends to perform very poorly if moisture is held against it with a lack of oxygen. The soot layer if kept in a moist dark area will accelerate corrosion.

[Sugarmaker]

I had not heard of this issue. Never gave the stainless pans much of a thought. I guess I would see if someone could Tig those or maybe solder??
Regards,
Chris

[TheNamelessPoet]

any idea what grade Stainless? 304, 316, 430(I think 420 is stainless)

I am not able to help much but I know different alloys of SS react differently to different corrosive "cleaners", coukt it maybe be that.

I sell parts to the food industry and they generally ask for specific grades of SS.

[TuckerMike]

The carbon on my pans is by no means "fluffy". I just spend about 5hrs scrubbing the pan to try and get the carbon deposits off. Easy-Off oven cleaner helped, but dtill took a LONG time. End result; I've got a few holes in the flue pan too.

I'm starting to think the problems I'm experiencing are a combination of two issues.

1) Using the chlorine bleach to clean the inside and possibly not rinsing it enough?
2) Leaving some of the soot on the bottom of the pan over summer.

When looking at the holes, there's definitely corrosion from the outside, but I can also see it on the inside too, just depends on which hole I'm looking at. I did find a welder that is going to try and spot-TIG the holes closed. Probably will only be a stop-gap measure for this season as I have a feeling more and more holes are going to start forming given the amount of corrosion I have seen. I just hope I can get the pans back in time to boil this season or else I'm going to have a lot of sap to sell.

I'll try to post pics in a minute.

[TuckerMike]

These pics are all from the bottom of the front pan.

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[TuckerMike]

Not exactly sure what grade stainless, but it's not magnetic, so probably 300 series.

[Cjadamec]

Those started on the bottom and worked their way up through the metal. How is the pan stored in the off season? It's classic pinhole corrosion caused by prolonged exposure to a warm and corrosive environment.

[TuckerMike]

Those started on the bottom and worked their way up through the metal. How is the pan stored in the off season? It's classic pinhole corrosion caused by prolonged exposure to a warm and corrosive environment.

Stored in my sugar shack (garage). Stays dry all year when not in use. Apparently I made the mistake of not removing all the carbon/soot at the end of the season. I brushed off the heavier soot, but didn't clean it down to bar stainless.

[Shaun]

I don't have any pictures of it yet. Stainless pans, welded. holes are in the bottom of the pans. For storage I did a citric acid soak and then did a chlorine rinse to kill off any "bugs" after letting it sit all summer. I thought I effectively rinsed it each time...but maybe not?

It is an oil-fired rig.

Probably not the entire reason but chlorine and stainless do not get along well. I have worked with chlorine injection systems and a small leak would eat a stainless hose clamp in no time. I had a 3x10 dg evaporator that had a sticker to not use Cholrine to clean, pans were 1995 or so.

[TuckerMike]

Shaun,

These pans are 1980's vintage. Not sure what alloy of stainless was used back then, but sure sounds like using Chlorine to clean it was a big no-no.

[Russell Lampron]

It looks like you've found what caused the issue and that you need to get your burner tuned.

For future cleaning use white vinegar to clean the inside of the pans and don't use chlorine. Rinse them at least 3 times and then again just before you boil. Don't worry about sanitizing the pans which is what I think you're trying to do with the chlorine. The heat produced when you're boiling is more than enough to kill any bacteria that might be there.

[buckeye gold]

Another reason I like the old fermented sap cleaning method. No cleaning solutions ever go in my pan. I may have to scrub some more, but that's ok

[Walling's Maple Syrup]

Looking at pics, I'm pretty sure the problem started on the underside of pans. You can see holes that are started, but not all the way through yet. Fairly certain it's from the fuel residue.
Neil

[Shaun]

Shaun,

These pans are 1980's vintage. Not sure what alloy of stainless was used back then, but sure sounds like using Chlorine to clean it was a big no-no.

I would definitely avoid it in the future but diluted and rinsed well is probably not going damage anything right away. I picked up a small 2x4 from that age and brought it home cleaned, scrubbed and shined. When I filled it with water and stepped back to enjoy my masterpiece it leaked like a lawn sprinkler. Just another lesson learned...

[TuckerMike]

It looks like you've found what caused the issue and that you need to get your burner tuned.

For future cleaning use white vinegar to clean the inside of the pans and don't use chlorine. Rinse them at least 3 times and then again just before you boil. Don't worry about sanitizing the pans which is what I think you're trying to do with the chlorine. The heat produced when you're boiling is more than enough to kill any bacteria that might be there.


It was an expensive lesson to learn for sure!

[raptorfan85]

Quick question, is this something that can happen burning wood? Or is it an oil burner issue?

[Cjadamec]

It's more of an oil burner concern. Not to say you are completely concern free burning wood. You should still avoid chlorine and store your pan in a dry place.

Another thing to consider is these pans are from the 80s so it took a very long time for these hole to develop. Nothing lasts forever.

[DrTimPerkins]

It can also occur by burning pressure treated wood or plastics (tubing) in the arch.

[tgormley358]

I’m just wondering if anyone can confirm generally, can pin holes like these come from not doing a thorough clean of the underside of the pan at the end of season? Mine is raised flu 5”. I haven’t don’t much For mine on the underside except a spray down and wipe, but it stays mostly very black and sooty. I’ve seen others here say they use oven cleaner.