Different CI cleaning question (electro?)

[mbellot]

Greetings all, quite a wealth of information you have here.

I'm working on a small cleaning project that has been giving me loads of grief, the cast iron grates from my grill.

I've managed to remove the food/grease/etc. with a couple evenings in the fireplace, but the rust and and (what I think is) mill scale is giving me real fits. I've even tried sandblasting a small section, but it takes a fair amount of time to remove the really hardened stuff. I'm not to worried about the "looks", since its not a collection piece, thats why I tried the sandblasting.

My questions:

Is the hard, black, layered stuff thats darn near impossible to remove mill scale?

If it is (or even if it isn't) will an electro cleaning dislodge it?

I have a good handle on the nuts and bolts of the cleaning process (and actually have all the bits except for the washing soda), but before I set it all up I would like some expert opinions.

I've attached a picture that shows one of the problem areas.

Thanks,

Mark

[Steve_Stephens]

I think it is what I call (but may not be) Mill Scale.  Sandblasting seems like a good way to remove it.  The cause is overheating of the iron which, on a grill, is an easy thing to do.  It the grill is only for cooking and not to have coals or a fire sitting on, the grill should never get hot enough to get the scale.  Burning pieces in a fire only cause more of the dammed stuff.  I would think that an electro setup would remove it down to good iron but those who use electro should know.

Steve

[ysageev]

[smiley=stupid.gif]

I have never had to contend with "mill scale" and in fact it is the first time I've heard of it.  My electro seems to remove everything and if it doesn't remove the scale I don't know what will without damaging metal.  

Correct me if I'm wrong, but think electro should remove anything from the iron that isn't conductive, no?  If the coating is conductive the hydrolysis will happen above the coating and not underneath it, thus not removing it...  That's my theory, anyway.  It is my understanding that electro cleans by the simple physical force of bubbles pushing from the iron against a coating, and that the cleaning is not chemical in nature, like lye.

[miniwoodworker]

I wouldn't worry about it.  :)

I have a charcoal grill with cast iron grates. While I don't have the scale problem to compare to yours, I think you'd be OK simply by sand blasting or using a wire brush to clean up the top of the grate where the meat sits. As soon as you have the top of the grate clean, start seasoning it. Coat the grate with your choice of cooking oil or Crisco. Build a low to medium heat fire in your pit and keep it running for a while. With a folded paper towel dipped in oil and held with a pair of tongs, continue to apply the oil for an hour or so. Let the grate cool down naturally.

If possible with your pit, turn the grate upside down and repeat the above. Turn right side up and repeat with a little hotter fire. Not hot enough to burn off the seasoning you've already accumulated, but with more heat, you'll really bake the seasoning into (onto) the metal.

As long as you get the top of the grate fairly smooth, the "crud" on the sides really doesn't affect cooking to any material degree. Cooking temperatures keeps the grate sanitized, so you don't have to worry about bacteria buildup in those scaley places.

After each cook, use a wire brush to scrape off accumulated cooking residue, while the grill is still hot. Apply another coat of oil. When you start your next cook, oil the grate again before adding food.

And, periodically oil the bottom of the grate, as the fire will burn off the seasoning. This step is to help keep more rust from forming.

There appears to still be a lot of cooking life left in that grate. So, good luck with getting the top smooth and the whole grate seasoned. Then, enjoy some good eating!

Edit: Grilling a meat with a lot of fat, such as chicken thighs, will speed up the process of getting a well seasoned grate. It'll take several cooking sessions to build up the seasoning to the extent that it really holds rust at bay. So, do try some grilled chicken for a few times. If you have a smoker/grill, Boston butts also work well for this dual purpose - grate seasoning and good eating, too.

Lee

[C. Perry Rapier]

The stuff you describe is exactly what electro does. No sandblasting, wire brushing, lye, elbow grease, sos pads, sandpaper, scraping, no whatever. Electro does leave on a black film that easily washes off with dawn dish soap and some water, if you want to light wire brush it to make it look like it was made yesterday, you can do that too, but if you just want to clean it, then electro it and wash the film off and you should be good to go. Thats my opinion and I'm sticking to it. And I've cleaned a lot of cast iron.

HOWEVER, if you do not want to cheat yourself out of all the fun then I would not recommend electro at all.

[mbellot]

The stuff you describe is exactly what electro does. No sandblasting, wire brushing, lye, elbow grease, sos pads, sandpaper, scraping, no whatever. Electro does leave on a black film that easily washes off with dawn dish soap and some water, if you want to light wire brush it to make it look like it was made yesterday, you can do that too, but if you just want to clean it, then electro it and wash the film off and you should be good to go. Thats my opinion and I'm sticking to it. And I've cleaned a lot of cast iron.

HOWEVER, if you do not want to cheat yourself out of all the fun then I would not recommend electro at all.

Thanks, but I've never been above a little harmless cheating.  ;)

So you think the electro will zap the scale as well? That would be truly sweet.

Lee:

The grill is (gasp!) propane. Having little kids and a full time job mandates simple grilling techniques for the week. I pull out the charcoal, hickory and the smoker on the weekends when things aren't too hectic.

I'm guessing the scale problem is a combination of high heat (trying to get the grates hot for steaks and such) and less than dutiful care on my part. I've been using PAM instead of Crisco, and after some searching around the web it appears that may not be the best idea.

I too am sure there is a lot of life left in them. If there wasn't (and I weren't so cheap) I'd just pop down to Home Despot and pick up a new set. But since I have everything to do electro already (except the washing soda) its a near zero cost to try.

If the stink isn't too bad I may get a couple seasoning passes on it in the oven to get things rolling, but if its too bothersome to the womenfolk I'm sure I'll be banished outside.


OK, so since electro sounds plausible can I get a little feedback on my proposed setup?

Rubbermaid bucket (7 gallon I think, maybe slightly bigger)
Several sheets of steel (not stainless or galvanized, it already has a bit of surface rust)
Steel wire used to tie rebar together at cross points (left over from building a shed foundation)
Lambda lab grade rack mount power supply, adjustable 0-60V 0-20A
Tap water and washing soda

Three of the steel sheets is almost exactly the same area as one grate, which seems pretty ideal.

I would put the steel sheets in the bottom, all tied together with the steel wire which is then brought out for the anode connection.

I would suspend the grate above the sheets with more steel wire, providing a cathode connection out of the water.


How does that sound?

[gt]

Hi Mark,

I'm not so sure about how good the electro will work on the red stuff but it will be interesting to see the results.

Your setup sounds good.  I would set the supply to 12 volts and mix in washing soda to get about 15 amps.

Gary

[mbellot]

Well I have it up and running, but now I realize I've got a couple additional questions.

1. Because of the size of the tub I'm using I can only electro one grate at a time. Is there some way I can temporarily treat (like canola oil) the first one to keep the rust off while I treat the second. I'd like to season them together if possible.

2. How critical is the amperage? If I set the power supply to 12-ish volts it only draws about 5 amps. In order to get 12 - 15 amps I need to increase the voltage to between 35 and 40 volts. Extra washing soda doesn't seem to affect this overly much.

3. I'm being over-cautious regarding the hydrogen gas, I'm set up outside. Is this really necessary? I'd like to bring it inside, but only if its going to be safe.

4. Any idea how long I should let it simmer before checking it the first time?

5. The water turned very black and murky within about five minutes, I'm guessing thats a good thing. Right?


Many thanks to everyone for their input, this looks like its going to be much easier than sandblasting and a wire wheel.  ;D

[gt]

Mark,

Without seeing you setup, I’ll comment on your on your questions as best I can.

1. If you dry it quickly, your first grate won’t rust while you clean the second grate.

2. The current limit at 5 amps occurs because the surface area of your positive and negative pieces is too small or the positive piece gets too rusty which limits the current.  Twelve volts is nice because the danger of shock is much less than with higher voltages.

3. I do mine inside in my basement but I have no data that says it’s safe.

4. I’d run it several hours and then brush it with a wire brush to see what its doing.  

5. Probably normal but I would expect to see a lot of red from the red scale on your grates.

Gary

[mbellot]

Gary,

Thanks. The water did turn a real rusty red in about half an hour and looks down right nasty now. Pretty much what I've seen in pictures of other electro setups at work. Hard to believe there is nothing hazardous in there, it sure looks deadly.

Would a warm oven work for drying the first grate, or just toweling off real well? I'm concerned that I'll do a less than complete job with all the various nooks and crannies and my red buddy will be back with a vengance. Would it be OK to "park" the first grate in another tub with just water and washing soda? I'm thinking the mildly basic solution might help prevent rust formation, but I could be totally wrong too. If I go the oven route it would probably be just preheated and turned off since its gas, the water vapor created when its on probably wouldn't help my cause...

Risk of shock should be pretty low even at 30 volts, which is where UL starts to get nosey about voltages. Anything below that and they are (generally) not so interested.

I was thinking about it, the current could also be related to electrode distance. They are a couple inches apart, probably more than necessary. I'd move the grate lower but I cut the steel wire a tad short.  :(

[Thomas_Callaway]

Well I have it up and running, but now I realize I've got a couple additional questions.

2. How critical is the amperage? If I set the power supply to 12-ish volts it only draws about 5 amps. In order to get 12 - 15 amps I need to increase the voltage to between 35 and 40 volts. Extra washing soda doesn't seem to affect this overly much.

Since you are using a variable power supply, just kick up the volts. I use one too and it depends on the size of your piece and the Ph of your electrolyte. (how much washing soda to X amount of water). If you put in a larger piece with more surface area, then you'll notice right away that you need less voltage to reach 12 - 15 amps. There has been some discussion that you get a better clean at lower amps (amps do the work), but that was for cookware. I don't think care outweighs speed in your case.

So... crank it up. Take a look after 3 or 4 hours. Sometimes I need to leave a piece in overnight so I just crank down the volts to draw 8 or 9 amps. Doesn't hurt a thing. I've left skillets, etc. running 3 or 4 days like that.

TC

[mbellot]

Thomas,

Thats one of the things that attracted me to electro cleaning. Most of the info I've read says that you can't hurt anything by "overcleaning" by days or even weeks.

Compared to the acid methods (vinegar, muratic, etc) its comforting to know you don't have to babysit it constantly.

I'll probably leave it on overnight and set up the second one this evening for swap out tomorrow night.

Thanks again for all the help.

Mark