Electrolysis in our dry kilns is giving us problems

CrazyHaole:

When ever there mild steel in the presence of aluminium an electrolysis can be expected especially when electric current is feed fro one to the other and if saltwater also then catastrophe result.

Separate the steel from the aluminium...apply anti-corrosive coating to steel and aluminium

It will be time consuming to relay enough information about this and I will have to it piecemeal--sorry.

The kilns(for the most part) are 6-80' long double track aluminum skinned, steel buildings--I was on the construction team and have a real good understanding of how they are assembled. The aluminum panels are sandwiched between two pieces of extruded aluminum, which are set on the a steel purling with a low grade stainless washer between them. The panels are pop riveted together with flashing. There are common steel frames on the interior side walls of these kilns which have a ground probe on each end(80' apart).

There are eight 15hp fan motors in each driven by a VFD. The fans, steam and heat are always changing.

I commercial fished on steel hulled boats for 15 years and have lived with electrolysis problems--Outside of catching fish it was our number one job, but we had it at a manageable level through diligence. I cringed while we built these kilns and had to bite my lip about the slip-shod construction. The time to address these problems(design and engineering) has passed, as far as I am concerned. They are state of the art kilns for this part of the industry and it seems that we have some unique problems with ours--Whether it is the wood that comes out of the saltwater or alder or both.

I will try to revisit them and take some electrical measurements later today.

I commercial fished on steel hulled boats for 15 years and have lived with electrolysis problems--Outside of catching fish it was our number one job, but we had it at a manageable level through diligence. I cringed while we built these kilns and had to bite my lip about the slip-shod construction. The time to address these problems(design and engineering) has passed, as far as I am concerned

True to a fault but may be you could effect a healing by replacing the stainless washers with zinc as a site managed anode of sorts.

What do you think...

Hi CrazyHaole

Not knowing what your setup is in detail I can only suggest to introduce an even lesser metal (lead,zink)that could function as a sacrificial anode/cathode. More details would help. Good luck. Ky.

If you're talking "robot jewelery" then you want to bolt large amounts of magnesium onto the steel. However, this being a dry environment, I think more could be gained by keeping the grounds very separated. That's just my HO.

Did you ever find out what the heck was eating your paint?!

Sorry to sound 'corrective', here (re-reading posts, again, it jumps-out at me that this point needs clarification).

Any time you have an "Anode-Cathode" combination in electrical contact, where an electrolyte may be present {even if only for intermittent, short periods}... ALWAYS paint your cathode (in this case, steel), but NEVER paint your anodes!!! (the alum).

If you do, you're just begging for pitting to occur on the aluminum, because NO coating is ever going to be perfect. NEVER.(period) [We're talking enamels, alkyds, epoxies, phenolics, etc. that you buy off the shelf ... not something one of you Coatings experts formed-up in the lab for a special/particular application!]

Stop the cathodic reactions from taking place, and NO anodic reactions will occur...! Corrosion at the anode can ONLY happen as fast as the free electrons are consumed at ('via') the cathode.

I posted a photo elsewhere on CR4 of a CS-SS combo exhibiting this heavy (undercutting-type) corrosion and pitting of the CS... "ALWAYS" & "NEVER"...!

Best regards to all ~

Hi CrazyHaole,

• What are the kilns used for?
• What is the purpose of the steel in the aluminum kiln?
• Where is the steel in relation to the aluminum?
• What is the evidence of the electrolysis on the steel?
• How does it show up?

A sketch one of the kilns would help a lot!

Sorry to ask so many questions, and I don't know this application. However, I have been around the block a few times and just may be able to help if I know the answers to the above questions.

Best Regards,

Mike

Steel touches aluminum you have problems. Stainless steel touches aluminum you have problems. Zinc coated steel touches aluminum you have problems.

The fact that the ground goes from the aluminum to the steel and THEN to ground, sounds like the perfect setup for electrolysis!!! Probably your best bet is insulation, but barring that, I say heck yes!!! Given them each their own very separate grounds.

And use phenolic washers too?

Use an insulting primer paint between the contact points of the aluminum and steel, and any attachment hardware.

Along with the primer use low resistance bonding straps attached to the aluminum and steel in several locations through out the structure and then run directly to a common ground rather than grounding each metal structure separately. This should help eliminate and short out the "battery effect" created between the dissimilar metals.

Another area to look at is the motors and controllers. Ensure that they are properly wired and grounded, and not grounded through the structures frame.

Good Luck.

I was told once that stray volts are like dogs, they will always get into trouble unless properly leashed.

If you do use primer paint, make sure that each surface is coated completely. A scratch in the primer only increases the corrosion process.

Hoi CrazyHaole

look here for a combination of materials (metals), if the tension gab is too wide you could add an intermediate material. (this will increase the electrical resistance)

http://www.qsl.net/n9zia/electrochemical.html

regards

If it's not practical to replace the washers with insulating ones, try cathodic protection. Dissimilar metals create a potential difference at the point of contact. This results in an electric which powers the corrosion. Cathodic protection places an equal and opposite potential at the joint. No voltage difference = no current = no corrosion. Bridges and other large structures often use this system.

Hmmm... some bridges do, in fact, employ cathodic protection ; BELOW the waterline, if they span water at all. "Large structures" that employ cathodic protection include... let's see: ships, drilling rigs, the BOTTOM-SIDES (only) of AST's (above ground storage tanks), that are in contact with the ground.

Let's give this fellow some real, honest-to-goodness advice. Sacrificial anodes aren't going to do a thing for you, unless you submerge your kilns. (Same advice for anyone thinking about buying a CP system for your car. Ain't gonna work unless you park it in Lake Michigan!)

Even an ICCP (impressed current CP) system won't push enough current through steam, or condensation-on-the-walls, to do any good at all.

CP does NOT put an "equal but opposite potential" ANYWHERE! CP delivers sufficient current to POLARIZE a structure such that the entirety of the structure is MORE ELECTRONEGATIVE than the otherwise most electronegative ("native") potential on that structure. By eradicating the inhomogeneities throughout the structure, local-cell action is eliminated!

Since we're limited to 4 options to help control the corrosion (below), he needs to figure out which of the 9 (according to NACE) types of corrosion he is dealing with, and then determine which method (or combination thereof) will rectify the problem:

1. Isolation (includes physical separation, insulators, protective coatings)
2. Inhibitors (for this app, inhibitive-type primers might be a slight help)
3. Environmental Control (not much control available in this case)
4. CP (which we said ain't gonna help).

...and, "electrolysis" isn't one of the 9 types of metal-corrosion, in the verbiage of corrosion engineers!!!

Michael Faraday taught us over 150 years ago that the corrosion of metals IS an electrochemical phenomenon ... and, that the amount of metal Lost is directly proportional to the amount of current that flows (from metal-to-metal), and to the amount of electrolysis that takes place in the water (or other electrolyte) surrounding the metals.

Every school-child in this country seems to come into contact with a grandpa, uncle, or old codger on the block who throws-out that term ('electrolysis') while packing bondo into his '65 Buick ... thus perpetuating in kid's minds that the proper term for corrosion is actually "electrolysis"...(!) ~Apologies for the rambling, but my biggest pet peeve is the Dumbing-Down-Of-American-Kids. It's got to stop SOMEWHERE.

More later ~ Best Regards to all!

Then again, sometimes we try to put technical information into a format that non- (or less-) technical people will understand.

You are, of course, correct that CP requires immersion. Since we do not know the environment, I was offering a possible consideration. I should have included the water immersion, though.

Electrolysis.............whilst I do not want to appear to to be pedantic, when one is speaking of corrosion.............there is no such animal as electrolysis.

Two types of corrosion, often incorrectly referred to as electrolysis are:-

1. Galvanic Action.........corrosion between dissimilar metals (refer to the nobility scale of metals)

2. Stray Electrical Current............usually caused when an electrical current goes to earth other than through a planned earth circuit.

What am I missing:

Oxidation of ions or neutral molecules can take place at the anode, and the reduction of ions or neutral molecules at the cathode. For example, it is possible to oxidize ferrous ions to ferric ions at the anode:

It is also possible to reduce ferricyanide ions to ferrocyanide ions at the cathode:

Neutral molecules can also react at either electrode. For example: p-Benzoquinone can be reduced to hydroquinone at the cathode:

In the last example, H ⁺ ions (hydrogen ions) also take part in the reaction, and are provided by an acid in the solution, or the solvent itself (water, methanol etc). Electrolysis reactions involving H ⁺ ions are fairly common in acidic solutions. In alkaline solutions, reactions involving OH ^- (hydroxide ions) are common.

The substances oxidised or reduced can also be the solvent (usually water) or the electrodes. It is possible to have electrolysis involving gases. For instance, fuel cells often use oxygen and hydrogen gases as reactants.

Re : "What am I missing" --- Perhaps the main point? These guys are talking semantics and trying to prove that if you want to get to the bottom of a mind boggling conundrum it helps to have a vocabulary that rises somewhat above your average rapper-cum-ebonics with a little "duh" here and a big "uhhh" there, + using the proper term when called for. You obviously understand that corrosion of metals involves redox reactions. Reduction at the cathode and oxidation at the anode. Hooray and congrats! You're among the elite handful. The rest will remain ignorant, or at best retain a vague comprehension of the profound truths, unless they are forced to learn the profundities lying hidden within the subtleties. In these posts, electrolysis isn't being referenced in the context of your wife's mustache removal. It's being incorrectly applied to (its part in) the corrosion of metals. I disagree, though, with stopping the dumbing down efforts. It's easier for me to keep selling tons of imported cr-p to newer generations who care more about the glossy finish (sitting on the store shelf) than either the guts inside the product, or the fact that the glossy finish will scratch horribly in normal use in their purse or pocket. Keep cranking them out for me!

Hi bwire,

Once again I probably did not make myself clear...............of course there is an animal called electrolysis...........however what I should have have said is that there is...................no type of corrosion called electrolysis.

My apologies.........it's just as well I think faster than I can type.............here bwire I know what I meant to say.......hahaha!!!!!

Hello MOBI,

Yes you were correct, the poster used a term improperly and I think each of us knew it was a terminology wrinkle. The term electrolysis was improperly used by GM in early 1960's to describe effects of using dissimilar materials in engine building, the corrosion occurring in the small aluminum block V-6's or I could be mistaken too

Thanks for courtesy

Hi bwire,

............the term electrolysis, just gets up my nose for some reason...............just one of my little idiosyncrasies.

I used to be conceited once....................NOW.....................I'm perfect!!!!!!

Chance would be a thing...............hahaha.

Part of the cause could be the electrical leakage from the fan motors. This is especially true when VFD are used. Make sure that the power cables to motors have a proper shield or at least a good grounding conductor as close as possible to the power cables. Metal conduits might be discontinuous. This ground wire must be well connected at the motor and the drive. I often visit plants where the motors grounding to the drives are not done correctly. In this case, the leakage current flows where it can which is often into the building structure, ground grid, or communication cables. Electrons are not choosy. They use the easiest path. Give them a good one that will not involve your aluminum building. Electrical insulation at the motors mountings can also help once you made sure that they are properly grounded at the drives.

Yep, marcot..............Stray Electrical Current!!!!!!!!!!

Although ac current is not usually too much of a problem............dc current is the main "killer" in corrosion.

My apologies for being tardy--I read through some, but not all your replies, and will go through them all.

Here's what we are talking about: www.coemfg.com/products/drykiln/

This whole problem is perfectly reactive to poor construction and design. I don't know how many times I have witnessed someone painting over rust and I have wanted to tell them that it's not just color.

Coating problems--These kilns go from ambient winter temperatures up to 190 degrees F. The purlings have torch cut holes for the stainless fasteners on the aluminum extrusions. The butt welds on the steel tubing aren't 100%, so whatever coating was there has been burned off with no real chance of applying new coating. Tons of shortcomings.

I looked into it a little further and took some more measurements. There is good continuity to ground throughout the steel and the aluminum--We lifted grounds and measured. If there is electrolysis and the path to ground made a difference-aluminum to steel to ground versus steel to aluminum to ground, I don't think there is any practical solution and I'm not sure that the rust and scale isn't deserved. I also found out that the reason we are looking at this as a problem is that there is an order for $20,000 worth of zinc bars(reorder after two years).

I set up quick experiment in our lab to meter dissimilar metals in liquid and found that grounds don't have much affect on the potential difference between them--I had to get back to work and left it there. I will revisit this in the lab as time permits.

In the meantime, I have a lot of reading to do! Thank you all and keep it coming if can.----Also, I don't know how the rating thing works and if it is customary to rate anything or all?

Why, pray tell, does your company have "$20,000 worth of zinc bars" on order...???

Are they going to make a giant zinc "Corrosion-god-idol" to pray to, in hopes of warding off this corrosion problem? ... surely THAT can't be it ... so ... they must be planning on making a hot-dip galvanizing tank, and disassembling the building one piece at a time for Galv-treatment, yes...?

I am serious as "the proverbial heart attack" when I stated that cathodic protection (whether sacrificial or impressed current) isn't going to be a worthwhile investment for the building components. If it was, rest assured that our Code of Federal Regulations writers would have taken that into account, when mandating protection of offshore steel structures associated with gas and oil production. [The mandate is for proper CP below the waterline, and appropriate protective coatings for areas above the waterline. CP will NOT work for atmospheric applications.(period) This is why the snake-oil "CP-for-your-car" systems are no longer permitted to be sold in the US. You have to order one out of Canada, if you're silly enough to!]

I reviewed many of the links at the site to which you pointed (coe mfg). Not many good pictures, but one (somewhat buried) paragraph jumped out at me:

"Coe's research team, also reviewing the insulation material currently used in kiln building, has determined the current rigid fiberglass to be the most effective. The foam type of insulation tends to absorb moisture vapor and become soaked with water. This reduced the effective insulation properties of the kiln building. Over time, a high temp kiln will loose a sustainable amount of the R-value found in foam insulation. The rigid fiberglass insulation, found in Coe kilns, does not absorb and retain the water vapor." I'm sure that you nailed the problem, when you mantioned poor design.

Can you provide photos of the exact location(s) of the worst offenses? [I admit: no clue as to what a purling is, architectural-wise; neither does dictionary.com nor wiki]

Best Regards to one and all ~

purling

Search in post and beam construction or wooden ship building structural members.

Re: (Definition of) "purling"

"Search in post and beam construction or wooden ship building structural members."

p o s t a n d b e a m c o n s t r u c t i o n o r w o o d e n s h i p b u i l d i n g s t r u c t u r a l m e m b e r s ===

pot

stop

tan

stand

standard

bandana

mean

meaning

coma

constrictor

constriction

truncate

narwhale

is it one of these...?

I don't see it yet, but how can you see audio oh maybe we when down through the boughs. On the sunshineday weoutsidefor meltorthawwithpurling soundofrippleof agua. Pulled thumbfromdikeandpurling ocurredaboveleak.

Try again

Did one mean to say purlin

A purlin is a horizontal member that lies across the rafters to support the roofing and strengthen the structure.

Thanks-a-gazillion, Mobi! A real GA to ya!

Modifying the Google search using "purlin" in conjunction with 'construction, architecture, etc, yields a plethora of valid results (link)... whereas all the searches in the world using "purling" bring-up a bunch of 'junk' leads (PURL sites, etc.).

Still looking for photos from the OP, with any additional details...

Tried to deter your course towards construction terms, Mobi gave the whole plate to you

Hi bwire

................don't ask me.................just seemed like a good idea at the time.

I must admit I had a great time as an owner/builder when we built our 100m² granny flat in our back yard...........as expected had a bit of trouble with the local council.

...........but by no means insurmountable............a bit of a power thing with the civil engineer.........probably works for the council because he couldn't get another job!!!!

I can't help being a smart arse.............it just come naturally.

Good luck one your problem. When you're ready to tackle the problems of reducing fuel costs and getting more constant drying contact me.

Hello All,

I work with CrazyHaole; This is just my two cents worth as I am no expert by any means.

Even though I originally thought that it was electrolysis I am having second thoughts now. Chris and I have had many discussions and I have been doing allot of research and I have come to the conclusion that it is a corrosion problem that is not related to current flow specifically.

There was some improvement using zinc where the steel structure sits on isolators on the cement footings, this is not where our major problem is. Instead we see the most damage at the door openings. When the doors are closed there is cold fresh air that leaks into the kilns around the edges of the doors. There are end baffles that seal the ends of the charge to force the air through the units of wood, this also creates a dead air space between the end of the charge and the door. All of the "bad" corrosion is occurring at this point. Because of this dead air space there is allot of moisture that builds up on the door frame and the doors. One thing to note is that the moisture is condensed from the water coming directly from the wood, it has a low PH and is considered acidic. I can tell you that some of the corrosion is from that condensed water dripping on the steel where it has actually eaten holes in the metal.

I have wire brushed and used a sanding wheel on the door frames primered and painted the steel with kiln coat (this is a tar based paint) and the corrosion keeps coming back. The tracks that the kiln carts run on are also corroding in the same area of dead air space. I have had to cap the rails with stainless steel using 309 stainless welding rod which has resolved the track problem.

Chris has already stated he didn't think that anodes were going to do much good and I think he is right; I think the answer is what he has already mentioned about stripping off the rust and painting.

Another thing to mention is that the serious corrosion didn't occur until we started running salt water logs. Again I am no expert but this leads me to believe that this is a chemical reaction and not electrical in nature. Also there is absolutely no corrosion where the different metals are in contact.

I hope this will clarify our situation.

Oh My! Got some good laughs--Prior to submitting my FOE-PAW(kidding, don't jump on me)--I checked the terminology of purlin and found it didn't exist, so I adjusted the query to -ling and found that didn't exist either. Next step was to add construction to the search and low and behold some boob sabotaged me by publishing this awful term that I took for gospel because I found it on the net. Forgive me--I will try to show more respect towards the anatomical terminology of buildings and materials.

Took some more measurements and found no resistance between structural components and some low AC voltage. Nothing really jumping out at me as far as I am concerned.

After reading MOBI posts, among others--Electrolysis is something I have re-thought and have resigned it to the same pit as purlin and purling for now and will continue to check these posts. I may be wrong but I think the moral here is--An ounce of prevention is worth a truncated narwhale.

OK. So, now I think I understand at least more about the kiln... Is this kiln for drying and/or seasoning logs/timber?

Hello Vermin,

Yes... We work at an Alder mill; the logs are processed into lumber of varying thicknesses. The moisture from different species of wood have different PH levels, for instance Alder has a lower PH level than Fir so it's water is more acidic.

As Chris mentioned there are eight fans, the air velocity is 800 fpm and the max temp. is actually 180 degrees. The RH at it's highest is around 90 percent and that is when we are removing free water from the wood, the temp. at this point would be between 150 and 170 degrees. At different points in the schedule the vents will open to maintain the the set points, when the vents open outside air is pulled into the kilns at ambient temps. So during the winter the air is colder than in summer and if I am remembering correctly the air is more dense in winter which would translate to more oxygen entering the kilns. Please correct me if I am wrong but wouldn't that support a chemical reaction as opposed to being electrical?

Again there is no corrosion at the dissimilar metal contact points. The only place I see rust is where wood dust collects and where water condenses or drips on the steel.

Brother

Years before I came to work at this mill, I tried to research a simple schedule for drying pine and juniper. I couldn't find anything to speak of. It is amazing how tight and proprietary information is on the subject.

Sounds like you're starting-to-begin to assimilate the reality here.

Given the fact that steel is slightly passivated in an alkaline environment, but subject to accelerated corrosion in acidic environments, you've got one factor of the equation.

The O₂ you mentioned does come-into-play: in atmospheric settings, the Reduction of oxygen is one of the predominant CATHODIC reactions (within corrosion Redox reactions ~ another area where "grandpa-advice" tends to obfuscate things!).

I still don't see any photos, or links to same... but I'm willing to bet that you're on the right track , eliminating Stray Current Corrosion as the culprit [MOBI was correct, that ac rarely contributes significantly to corrosion. There are certainly exceptions.]

I haven't seen, yet, how y'all deal with eliminating the biggest factor in the equation: the humdidity...?

There are some enormous dehumidification units on the market; oftentimes wheeled-around in vans, for Paint & Protective Coatings applicator's use. Do your kilns incorporate such process while running...?

Wishing Success ~

Apologies for the images, but they are not my kilns and this business is very competitive and the kiln information is horribly proprietary. I did give the link to the kiln manufacturers site.

www.coemfg.com/products/drykiln/

They don't volunteer much information, though. It is the going rate in this industry-The cheaper the better.

I just got done with another tour of measurements(all for nothing now, as far as I am concerned). I have way too many other things to keep running here and it doesn't look like we can improve anything electrically or by adding grounds.

When I followed your original link to Coe's site (your post, #20), I thought you were referring us to look at something "Similar-To" what you had built yourselves (as your statement in post #2 led me to believe: "I cringed while we built these kilns...".)

So ... now that I clearly understand that you are dealing with something that was "Purpose-Manufactured" for the job ... the manufacturer's "Customer Support" page states:

"Coe Newnes McGehee (CNM) provides solutions through expert technical assistance, authorized replacement parts and machine upgrades. We are dedicated to providing products and services that will ensure reliability and enhance the performance of all your mills' systems throughout their lifetimes. CNM Customer Support Representatives are committed to work as a part of your team to achieve a high standard of service."

Did their original warranty state a "Maximum Chloride Content" for the water being removed from the lumber placed into the kilns...? Did you follow their construction instructions to-the-letter...? If they put so much research & development into these things, why do they rust-through like a '55 Chevy in the Snow-Belt? (Detroit was one of the first biggies to spend big-buck$ on proper anti-corrosion engineering. There is legislation currently pending, to provide tax breaks for companies to protect their assets against corrosion, which eats billions of dollars per year from our GNP)

I'd look into whether there's ANY sort of "Performance / Reliability Warranty" in effect, and what sort of remediation help they are willing to offer, in order to bolster their image.

Best of luck to y'all ~

Hello ndt-tom,

Humidity in the kilns is an integral part of the drying process so total or even partial elimination would be out of the question.

There are some kiln designs that pre-heat the air before it enters the kiln through the vents although I don't think the reasoning is to reduce O2 as much as it's for controlling temp. drop in the kiln.

I will try to remember to bring my digital camera in so I can get some pic's to post.

We do appreciate all of the help.

Brother

They also tout R and D with aero-space engineering, but if you go into the older kilns we have, I don't see any changes being made at all. The upgrades are purely control system related.

Okay now you've rendered the situation to have only a corrosion at the door frame, that's what I'm hearing. I suppose you could sand, brush and repaint often or change the door design. Possibly to that more often found aboard shipping vessels commonly know as a water tight hatch. There's my two cents...

Hatch what?

Open and shut