Eric talks about the difference between the valence states of the chlorine atom. Cl+ is different from chlorides, which are Cl-. Chlorides are inert, but they can be recharged into chlorine gas with a salt chlorine generator, and they also interfere with stainless steel's chromium oxide layer, helping chlorine corrode it.
00:00 - Introduction
01:21 - Halogens on the Periodic Table of Elements
02:48 - Valence states
06:17 - Chlorides and stainless steel
09:44 - Closing
168. What are Chlorides?
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[00:00:00] Eric Knight: Hey everybody. Welcome back to the Rule Your Pool podcast. This is episode 168. Getting back into pool chemistry after a few episodes of not doing so. I'm your host Eric Knight with Orenda and HASA, and happy new year. I took some time off around Christmas and afterward. As this episode comes out, we are in the thick of trade show season. So I'm going to try to get one out every two weeks, but it's definitely not going to be every week just because the travel is pretty much non-stop. So sorry in advance.
[00:00:30] In today's episode I'm going to talk about chlorides. We've mentioned chlorides a lot in many other episodes before, and to be honest with you, I didn't really spend the time to investigate what they actually were. Other than Cl-. You know, in a chemical formula.
[00:00:47] They're inert, they don't really hurt anything, but they do impact corrosion, specifically of stainless steel. And we talked about that in I believe episode 164 and 165, when we talked about corrosion. We also talked about bromides in episode 114, when I was talking with Terry about understanding bromine.
[00:01:06] We're going to talk about a little bit of both because I learned some things as I was getting through the revision and proofreading process of these corrosion topics that we were talking about in the past few weeks. This is episode 168. What are chlorides?
Halogens on the Periodic Table of Elements
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[00:01:21] Eric Knight: Okay, let's start by looking at the periodic table and we're going to go over to the halogen gasses, where you have fluorine and then underneath it, chlorine, bromine, and so forth. These halogens, while they have some disinfection ability, as we know, also create salts.
[00:01:59] Terry Arko talked about this in episode 114 when we were discussing bromine. So sodium bromide is the bromine salt. Sodium chloride is table salt. That's what we're all very familiar with. If you have a salt water system, that's what you add into your pool so that the salt chlorine generator can conduct electrolysis and create chlorine.
[00:02:21] If you remember from that bromine episode, the bromide ions never go away because they get recharged by an oxidizer like chlorine, or hopefully not using a secondary oxidizer like ozone or AOP, because those will create bromate ion, which is a separate conversation. But go back to episode 114 to listen to that. The point is an oxidizer will recharge the halogen below it.
Valence states
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[00:02:48] Eric Knight: So what are these chlorides? And what are these bromides? We first need to understand the element itself. It's a halogen gas. There can be different valances, meaning charge. So if you have just Cl, that's not natural for how chlorine is because if you ever see chlorine, like elemental chlorine, as we say, it's a Cl2. Kind of like elemental oxygen is also O2, because an O1 is unstable.
[00:03:15] In fact, how ozone has created is you often split the O2, and you get these O1's that bind to other O2's to create O3. And that's ozone. It's unstable, it's a radical, it's not something that wants to be that way. It wants to find balance. And anything in nature is going to look for balance.
[00:03:33] There are different forms of this chlorine atom. If it has an extra proton, if it's positively charged, we're just going to call it chlorine atom. That's Cl+. But if it's negatively charged, if it has an extra electron, it's going to be chloride ion. A chloride because it's negatively charged, cannot take on more electrons. It cannot oxidize. But a positively charged one can. Because it's got that extra proton, it is looking for an electron. And so it's going to oxidize.
[00:04:06] I'm going to give you two examples of hypochlorous acid and hydrochloric acid, also called muriatic acid. Let's look at the valences of each atom in HOCl. So you have a hydrogen, you have an oxygen, and you have a chlorine. All right. The H, as we know a Hydrogen ion is positively charged. We talk about this a lot with the pH discussion. So it's H +1. And then oxygen actually has two electrons. So it's -2.
[00:04:41] H +1, Oxygen -2, which means it's a net of minus one. So it's looking for something positive. And it's going to have chlorine in that +1 state. That's how it stabilizes. So it's H +1, O -2, Cl +1. That makes HOCl. So you have a chlorine present in there. Now, if I'm going to oxidize something, like HOCl does, it's going to swap that oxygen and take on electrons. And those electrons are negatively charged, which reduces the chlorine. It reduces the valence. We talked about this in our ORP episode. It's going to reduce it down to HCl, hydrochloric acid. Now remember the H is a positive.
[00:05:27] So it's H plus, which means. That the chlorine in there has to be in its negative state, which is a chloride. H+, Cl-. So when that splits apart and dissociates in water, you're going to get chlorides.
[00:05:42] Chlorides are left behind by all types of chlorine because of this process. Chlorine dissolves, it becomes HOCl. It then gets reduced when it kills or oxidizes into HCl. Which, by the way, is why liquid chlorine, and cal hypo are net neutral pH or very close to it after they do their job. Not immediately, but once they do their job. Once they kill or oxidize, they bring their own pH back down. This is why. You're creating your own muriatic acid. That dissolves in water and you get chloride ions left behind.
Chlorides and stainless steel
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[00:06:17] Eric Knight: Chlorides are inert unless they're in the presence of stainless steel. And the reason for that is stainless steel has a chromium oxide layer with something called molybdenum in it.. I think I said that, right. I don't know how to pronounce it, honestly. But this chromium oxide layer in particular gets affected and interfered with by chlorides.
[00:06:38] Chlorides themselves are not corrosive, because again, they don't take electrons. Go back and listen to episode 164, metal corrosion is just a metal losing electrons. That's all it is. And if a chloride can't take more electrons, and it cannot, it cannot corrode. And I think I'm misspoke in episode 164, because I didn't realize that it wasn't just the chlorides doing that. It was actually chlorine in its positive state.
[00:07:06] Here's what I mean by that. Think about chloramines. Something I'm deeply familiar with. Hell, chloramines are the reason I'm in this industry because I got sick from them. Nitrogen trichloride, also called trichloramine, is what off gases into the air along with several hundred other byproducts like cyanogen chloride.
[00:07:24] So nitrogen trichloride sounds like it would have chloride ions in it. But if you look at the valences of them, they actually have chlorine in them in a plus one state. I didn't realize that. I guess I always assumed based on the name that well chloramines, they get into the air, especially in an indoor pool, condenses on metals, and then it corrodes them. Because it leaves chlorides behind.
[00:07:50] Well, I'm not wrong in the sense that that's what's happening. What I am wrong about is the valence of that chlorine in the chloramines. What's happening is the chlorine in the trichloramine is oxidizing the metal. And when it does that, it gets reduced into hydrochloric acid. Again, just like chlorine. Creates this own muriatic, which further accelerates the corrosion. And then it gets reduced to chlorides which further interferes with the chromium oxide on that stainless steel. And this is why chloramine vapor in the natatorium that condenses on metals creates these orange rust spots. It's a huge problem in indoor pools.
[00:08:34] made the mistake of just assuming it was chlorides. I just never looked deep enough into it. And just, I said it generically. Kind of like most pool operators that deal with indoor pools, they just use the term chloramines generically to talk about all the stuff that off gases from a pool. Technically there's a lot more than chloramines. But we just call it that because it's simpler.
[00:08:55] So. Let, let me rein this back in. I'm going on a tangent. I don't have show notes for this. So the only thing I have is a list of my episodes in front of me. Chlorides are inert Cl- that cannot take on electrons. So they can't oxidize and they can not corrode. They can't kill. They can't do anything. But they can be recharged with electrolysis in a salt chlorine generator, and they can attack the chromium oxide layer on stainless steel. So they're not completely inert. Uh, they just are for pretty much everything else that we deal with.
[00:09:29] Chlorine atom is a Cl+, and that's what you find in hypochlorous acid, that's what you find in chloramines. Trichloramines, anything with disinfection strength. And that's what is going to actually do the oxidation because it's looking for electrons.
Closing
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[00:09:44] Eric Knight: So I hope that doesn't confuse you too much. Any type of chlorine eventually will get down to chlorides. These chlorides will show up on a conductivity test. They will show up as part of TDS. If you have more chlorides, these numbers go up. So as you accumulate them over time. Yes, you will have an increase in TDS. And that's regardless of what chlorine product you're using. Account for that.
[00:10:09] There is no way to get them out other than reverse osmosis filtration and draining and diluting. So they're not really a big deal until they get to levels that are going to complicate your LSI or are causing a corrosion issue.
[00:10:23] Generally speaking, if you have too much in a salt water pool, the salt system is going to have an issue. Depends on your manufacturer. Some of them say, don't go over 4,500 TDS. Consult the manufacturer on that. You don't want too much of this in the water, because then you don't get enough electricity going through it. So just keep that in mind. Um, And I think that's all I have to do with chlorides. We got a few other topics to get through this spring.
[00:10:50] One final note before I go. As a reminder, January 27th, the day before the Northeast Pool and Spa show, I'm teaching the Watershape University Essential Water Chemistry class. That's Service 1211. It's an eight hour accredited certification course. It's kind of the culmination of everything I've been teaching for the past eight years. Comes with a book. And you're going to be able to take that book back with you with your own handwritten notes in it. I put in the better part of 2024 creating this class from scratch to make sure that it is worth your time.
[00:11:22] And if you just implement like 10% of what you learn, you're going to notice a big difference and to improve your ROI on that class. It is an investment of $800 to Watershape University. But, uh, we hope to see you there. So far, really good attendance. We do have some more seats left as of today. But, uh, we're trying to pack it out. So we hope to see you there in Atlantic City on January 27th.
[00:11:44] And for the west coast people at the Western Show, teaching that class again, February 6th. That first day of the Western show. Cause I think the expo opens like an hour or two after we're done with the class.
[00:11:57] It's eight to five, lunch included. Uh, same with the Northeast show. Hope to see you all there. Thank you so much. If you have any questions about chlorine versus chlorides or any of these byproducts, let us know. The help center is ask.orendatech.com. And you can ask me a question if you want, just email podcast@orendatech.com.
[00:12:16] I'm your host Eric Knight with Orenda and HASA. This is the Rule Your Pool podcast. Episode 168. And, uh, yeah, that's all I got. Happy new year, everyone.
[00:12:26] Thanks.
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