CTSP Episode 177 - AWWA D102 - Outside Coating Systems for Water Tanks

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Brian Cheshire joins Jack Walker and Paul Atzemis to discuss the AWWA D102 standard as it relates to coatings for the exterior of water tanks. They discuss factors relating to the industry, coating choice, surface prep, and more.


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Jack Walker: Welcome to another edition of the Carboline Tech Service Podcast. I'm Jack Walker. With me is Paul Atzemis. And we're going to start this show off just the two of us before we kick to a great interview with Brian Cheshire about AWWA D102 and the outside systems for coating water tanks. But we kind of have a major announcement to make.

Paul Atzemis: Yeah.

Jack: And, Paul, do you want to tell the folks?

Paul: Well, we've got some real big changes coming to what Jack and I are doing – the kind of things that we're putting together and some of the activities that we're undertaking. And it has developed into a bigger project maybe than we thought it was going to be to start with. So, we want to make some changes in how we do some of the things. Doing that means we're going to change the release schedule of the Carboline Tech Service Podcast. We're not stopping it. We're just changing the release schedule so that we can add more content, at more different devices, on more different platforms.

Jack: Yeah, it's really an addition by subtraction. So, starting in April, we're going to come out with a new podcast on the second and fourth week of the month. So, we are going to reduce down to two a month. This gives us the time to really put in the effort to the episodes that they deserve, especially now that we've explored and gone on YouTube. Because with YouTube, there's a little bit more work there, and we can make them even better than they currently are. So, this isn't a reduction because of anything other than we need to be able to provide even more content for you guys and improve on the content that we are currently creating. And this is episode 177, so that's 177 weeks in a row.

Paul: Right.

Jack: You know, I want you guys to all hear us. This is definitely a good thing as we move forward.

Paul: Right, because really the alternate was, we go into seasons, like you see in television shows, where we may only have new content for eight or ten weeks, and then it's all reruns for the next eight or ten weeks. And we decided it would be better to do them every other week and keep new content rolling, just doing it in multiple platforms.

Jack: Yep, so with that, here's our interview with Brian Cheshire about AWWA D102 – Outside Systems for Coating Water Storage Tanks.

Introduction to Brian Cheshire and Water Tanks

Jack: And like we do frequently, we are joined by Brian Cheshire. Hey Brian, how's it going?

Brian Cheshire: Hey! Good morning, guys.

Paul: Morning, Brian!

Jack: Like we do with Brian always, we decided to talk about different water/wastewater topics. And this week is no different. We alluded to this standard a little bit in our last episode when we talked about AWWA C210. We talked about how AWWA D102 is now referencing AWWA C210. So, we thought it'd be a good idea to take some time and talk about AWW D102. Now this standard, primarily…

Paul: I was going to ask, "How many times are we going to be able to say AWWA without messing it up?". But you already proved we hit that limit because you forgot the "A" on the end of that one.

Jack: Did I?

Paul: Talk about…

Jack: I thought I was on a roll.

Paul: I guess that was our limit. What, we say it five times, you said it in the first 30 seconds?

Jack: Arr, do I have a mouse in my pocket? Anyway. AWWA D102 deals with water tanks. And so I think it's a good idea to set the stage and talk about a little bit of background as it comes with water tanks. Brian, do you want to give us a little bit of information about water tanks?

Brian: Yeah, sure thing, Jack. And hey, I was going to say before answering that, it's refreshing to see that other people have a hard time saying AWWA multiple times. You know, I thought it was just me and my Southern accent. And you know, sometimes we struggle with annunciation down here and…

Paul: Well, it probably is that too, but…

Brian: Yep, probably didn't help things, but…

Paul: No.

Jack: Not touching it.

Brian: Well, and another thing that probably won't help today, I guess this is what, our third podcast I've done on here on video?

Jack: Yeah.

Paul: On video? Yeah, probably.

Brian: Yeah, and so basically, this will be the first one that I don't have you guys minimized. Because I was too worried before, you know, how am I going to talk and look at these guys and see they're little back and forth banter and all? But after watching the last episode, I learned my lesson, and I was like, you know, I need to keep an eye on these guys, you know, moving forward and all their shenanigans.

Jack: I got nothing. I plead the fifth.

Paul: So, the good part is that we have Jack on our side, and he can edit out the things that we don't want anybody else to see. And, you know, maybe dropping a little graphic here or just do some fancy clipping of the video and be able to make us look more professional than maybe we really are.

Brian: There you go. Any little bit helps, but...

Paul: That's right.

Brian: You know, but talking about water tanks and in coating water tanks specifically, kind of first want to kind of talk about, you know, water towers in general. They've really been part of community water systems for quite some time. I mean, there's several water tanks in the US that have, you know, have eclipsed the century mark - some that have been in service since the 1800s. You know, while doing research for this, kind of an interesting fact, you know, where you guys are in St. Louis, there's actually three water towers just in the St. Louis system that are on the National Register of Historic Places. So, Jack, if you need somewhere to go this summer, you know, when the kids are out of school, you know, you ought to check that out.

Jack: Take the historic water tank tour? We got three right here. I mean, I can't think of anything more exciting.

Paul: That's right. Your kids would love you for that one.

Jack: Dad of the Year, right here.

Paul: That's right.

Jack: Yeah.

Brian: But water tanks are used both for, you know, really drinking water storage and then also for fire protection. And you'll see different construction types. You'll see, you know, ground storage. You'll see elevated tanks. But really, when you talk about coating them, you know, a lot of the considerations remain the same. There may be various reasons that you want to coat the outside of a water tank. You know, obviously corrosion protection, aesthetics, graffiti-resistance. Because let's face it, I mean, you get in a lot of these rural areas, you know, like the song says, you know, Billy Bob may want to spray paint that he loves Charlene on the local water tanks. You know, being able to have some resistance to that is helpful. But really, water tanks serve almost as a billboard for a lot of towns. And, you know, when the coating system is degradated and looks bad, it's a natural thought for some people to think, "well, man, if they outside that tank looks so bad, I wonder what the inside of it looks like, you know, which contains the drinking water that I'm partaking of." And then also visitors, you know, traveling down the interstate, come upon an exit, and you look, and you see a dilapidated water tower, whereas one exit down may have a beautiful water tower. You know, it really says a lot about the communities. So, some of that definitely comes into play.

Paul: I remember as a kid growing up, there was a water tower on the highway exit, two before my town. We didn't have a water tower at the exit, but two up did. It was beautiful. It was a carousel that went all the way around it that they had painted on it. And it always let me know as a kid, "oh, we're getting close to home" because I would see that and know, oh yeah, two more exits, and that's ours.

Brian: Yep.

Introduction to AWWA D102

Paul: Yeah, so as we talk about these a little bit, why don't you give us a little bit of the background? You know, we're talking about AWWA D102, which is for welded steel tanks. Why don't you tell us a little bit about the history of where this came from and the background on the standard?

Brian: Yeah, sure. So, you know, interestingly enough, the first iteration of this standard was approved in February of 1964. And so, really, ever since then, there's been numerous revisions to it. Currently, you know, we're working with the 2017 revision. However, there is a new revision that's currently getting finalized that we should see very shortly. But typically, these revisions are handled by a committee of personnel, and it really is a good cross-section of the industry. You have coating manufacturers, tank fabricators, engineers, and then even some key owners included in that. But really, some important thing, it's very much so like C210. AWWA explicitly says, you know, these are minimum requirements, but it's not a specification. Use of this standard really is purely voluntary. Really, the local conditions are going to supersede this. But it is a good standard, you know, because it does lay out really some minimum requirements. I'd say another misnomer about it is, you know, some people look at it as almost a QPL or an approved products list. It's not necessarily that either. There's a lot of other referenced standards that it kind of touches on too. You know, we talked about C210. You even mentioned C222. But I would say probably the one that it works the closest with is NSF 61, you know, because naturally, anything that's going to be used on the inside of a water tank has got to have NSF 61. But I know today, you know, we're really going to be talking about the outside coating systems, you know, because that's another thing the standard does, it explicitly breaks out outside coating systems and inside coating systems and really gives you some different suggestions for each, you know, and lays out those minimum requirements to meet those.

Outside Coating Systems (OCS) Per AWWA D102

Jack: For sure. So, let's take that a step further and look at some of the systems that we see more prevalently today when we're coating the exterior of a water tank.

Brian: Yeah, so I would say really your OCS or outside coating system, you know, as it's referenced in the standard. You know, the first several are going to be the ones that you don't see quite as often, like your alkyd systems and all. But I would say, over the last ten-fifteen years, we're seeing more and more of the ultra wearables or, you know, the longer service life type systems, first of those really being OCS-4. And that's going to be comprised of an inorganic or organic zinc-rich primer. You're going to have an intermediate coat of aliphatic polyurethane, and then you're going to have a full finish coat of fluorourethane. And then, typically, you'll even see logos on top of that also with the fluorourethane. But, you know, kind of talking about some of the other standards. You know, some of the zincs or pretty much all the zincs in these outside coating systems are suggested that they be in accordance with SSPC-Paint 20. And then most of the polyurethanes that you see called out, they suggest that those be in compliance with SSPC-Paint 36, which I know you guys have talked about, you know, on past episodes here.

Paul: Yeah, we sure have. We've talked about both of those in previous episodes. Yep.

Brian: But OCS-5 is kind of the next one. And that first coat, an intermediate coat of epoxy, and then a finish coat of aliphatic polyurethane. And for the epoxy, as I mentioned a few minutes ago. It's not a requirement necessarily, but it is suggested that epoxies meet C210. That is another thing worth mentioning. And then I would say OCS-6 is the other one that I see used quite a bit. That consists of an organic or an organic zinc-rich primer. It's got an intermediate coat of epoxy and then a finish coat of aliphatic polyurethane. And I would say, you know, this is a very common system seen on water tanks. But, Paul, I know you field a lot of calls with Tech Service, and I would say this is probably a bread and butter, you know, staple system, really across all industries for atmospheric service.

Paul: It really is. And one of the things that a lot of companies do, I know Carboline does it, and some of our competitors do it as well, is you try to make it as easy as possible. And although you don't need an NSF coating for the outside of the tank. That's frequently the same one that they use. That way, they know it's the same size on the inside as it is the outside. And they know how much paint they're going to need, and they can bring it in and put two or three coats on the inside, put two coats on the outside. It's all the same materials, same equipment. The painters know it. They're used to it. They understand it. It really just makes the job flow. Once they're familiar with the product and they understand it, the projects usually go much better at that point. So, it's not uncommon to see them use the same one inside and out.

Brian: Definitely a great point there. I would say kind of before we close out talking about the outside coating systems, you know, there's a few things worth mentioning that, you know, kind of fall outside the scope of those outside coating systems but are still used quite a bit. But the first of those is, you know, polysiloxanes. While they're not currently included in an OCS, those are used quite a bit as a topcoat on tank exteriors. You know, I mean, these materials, you know, and we've talked about these too, on here before, but you know, they're isocyanate-free. They're typically a little higher build. They really have very good weatherability, in some cases, can rival fluoropolymer.

Paul: And you know, one of the things, and we mentioned it earlier in this discussion, this is a minimum set of requirements. So, anything that specified a urethane, typically a polysiloxane, will get that much or better. So, you're free to substitute a superior product in any of these specs as long as you're meeting the minimum required. And required is even a loose term because, like we said, this is a set of guidelines. And so, substituting in something like a polysiloxane may be a perfectly suitable alternate in some of these scenarios.

Use of Fluoropolymers for the Exterior Coating on Water Tanks

Jack: Yeah, I'm actually kind of surprised that there isn't a standard specifically for polysiloxanes considering the amount of use you see of those products in the industry. Speaking of fluorourethanes, Brian, I know a lot of times, you know, because these are the ones that provide us the best weathering, even more so than the polysiloxanes, even more so than the polyurethanes. A lot of times, though, you see that guys maybe just do the label or the town name or something like that, in the fluorourethane or the logo. Do you see use outside of the logo with those fluorourethanes on water tanks?

Brian: Yes. I mean, as we mentioned a minute ago on the outside coating systems, you know one of those does actually incorporate a full finish coat of fluoropolymer. And I mean, you see in some areas, I mean, I know you get up into the Northwest, and heck, even in some municipalities where they don't necessarily want to see the water tank, sometimes you'll see tanks done in a dark brown or a dark green, you know, something to kind of camouflage it into the background. And as you know, those types of colors are more susceptible to fading. And so, I see fluoropolymers used in those instances quite a bit. But you're definitely right in that they're used predominantly for the logos and for the bolder colors, just because of the long service life and really because of the cost of them. Some municipalities may not be able to do the full tank with that expensive finish coat.

Paul: And you know, the same is true when you get into higher elevations. The effects of the sun are higher in how aggressive they are towards these kinds of coatings. And frequently, you'll see a lot of fluorourethanes used in those atmospheres as well, just to help get them over that hump of "how many years am I going to get out of it?" It's worth a few extra dollars for the coating to be able to get those extra years out of the system.

Brian: Agreed. Well, Paul, one other thing, talking about outside coating systems, so the D102 standard really talks about new tanks and then recoating tanks. One of the things that is mentioned in the document, it's in the appendix, I guess, is the best way to say it, but there are some guidelines, I guess, for overcoating. Because there may be some instances where, say the municipality, may not have the time or the money to do a full blast containment and recoat. And I know they suggest SSPC TU 3 as a good standard or good guideline to kind of look at when you talk about different criteria for overcoating. But do you have anything to add there, kind of some best practices that you see? Because I know, once again, you take a lot of calls from, you know, from the industry.

Surface Preparation for Maintenance Systems for Coating the Exterior of Water Tanks

Paul: Yeah, so I mean, there is a lot that's covered in that document, and it's a well-put-together document as a reference. Really what you want to look at, like any system. I know typically, you know, when you're at home, most people think, "oh, I paint the wall because it's dirty," but that's not how we want to treat an industrial coating system. You want your surface to be clean to start with. So, whenever you're looking at these, if you have to do an overcoating, you want to start with it clean. If you're able to do any sort of abrasion or etching, that's always going to help improve your adhesion of whatever topcoat you put over it. And it might be by the detergents that you use. You know, there's a lot of companies out there that make some etching cleaners that damage the existing coating, but they do it to create some porosity so that the topcoat sticks better. If you can't do either of those and you can't blast, you can't abrade it. Then you're looking at something "I need an adhesion-promoting primer, something to help make a suitable overcoat system." And every paint company has them. We have our own. And they typically are applied very thin. And then they allow you to put a new color stable topcoat is usually what you end up doing, whether it be a urethane or a fluorourethane, polysiloxane, those typically will go over those. But clean, dry, sound, you need to make sure that you have good adhesion of the existing system because if there's any weakness, it's going to be when that new coating system is applied and applies the stresses of as it cures, it shrinks up. Most of the time, we're talking about solvented coatings, whether that solvent is water or traditional solvent, xylene, MEK, whatever it is you're looking at. As those evaporate out of the coating, they shrink up. When they shrink, they add stress to the coating system. So, if the existing system is not tightly adherent, it's going to break loose. Any defects will be emphasized at those points. So, you want to make sure it's in good shape. Anywhere where you have damage or loose coating. You need to remove those, whether that's scraping, sanding, power tools, you remove those, and you want a clean sound substrate to start with. So, that's usually your starting point. But most of that's covered in the TU update as well.

Jack: Well, I was going to say every blast cleanliness standard starts with clean and dry.

Paul: Yep.

Jack: And so, you know, sometimes we can get around the dry. There are some coatings that cure underwater. There are some coatings that do well with sweaty situations, but clean is hardly ever going to change. Because if you don't have your substrate clean, you're never going to have good adhesion and good performance from your coating system.

Paul: That's right.

Jack: So, as we look at this standard, Brian, is there anything else that you'd like to discuss?

Brian: As I mentioned, you know, we've just touched on outside coating systems today. You know, the next time I'm on, I'd like to take a deeper dive into the inside coating or lining systems that are included in this.

How to Use the AWWA D102 Standard

Brian: But I would say, you know, I mean, when you're coating the outside of a water tank, there's a lot of considerations, a lot of things that come into play. I would say, as a specifier, D102 is definitely a great standard to reference just because it is, as I alluded to earlier, it's something that's hashed out and voted upon by a really good cross-section of the industry. And they do a good job of covering a lot of the different aspects of a coating project. We just talked about the coating systems today. But I mean, it takes it a step further and talks about surface preparation, talks about inspection, some quality assurance, and quality control measures that can be taken. But I would say, you know, kind of another thing to consider. You hear a lot of talk about sustainability and lifecycles of coating systems now—definitely a big buzzword across all industries. And if you can spend a little more money on the front end and get a system that lasts longer, that's going to be less frequent repaint. So, less intrusion. There may be instances where you've got to contain, and you've got to disrupt a community. So, sometimes it may be beneficial to spend that little extra money on the frontend for a longer-lasting system, just to where you don't have to address that later. But there is a good NACE paper that's referenced quite a bit. It talks about the expected service life of coatings. And I did want to point out when you get into the atmospheric section, it actually calls out some systems and actually references some of the D102 OCS systems there. And so another good reference document, if you kind of want to see what that service life may look like there.

Wrap Up

Paul: Yep. And we did several podcasts on that one as well, so that you can go back and listen through those and pick up on some of those topics like Brian pointed out.

Jack: Absolutely. Well, I think we've reached our time limit, so Brian, thank you very much for coming on.

Brian: Thank you for having me back, looking forward to it again.

Jack: Absolutely. And the thing that we just want you to remember about this week's episode is that AWWA D102 covers both inside and outside coating systems for the coating of water tanks. So, there's always multiple different ways to do this, like we've discussed in the show. This just kind of gives you some industry-like guidance. So, for Paul, I'm Jack, and we'll see you guys next week.