@hube268 How is your deep ROV deployment developing?
Any signs of corrosion or all good? Would you mind sharing a few more details on how you went about connecting the anodes to all relevant components?
“terminal rings” are stainless steel crimp type with stainless steel wire in between I suppose? Did you just crimp them or did you do any potting / glueing on them?
Are you using standard stainless steel screws on the end caps? And did you connect every single screw on the end caps and lumen lights or just one of each component?
Did you do any calculations / voltage measurements for figuring out the size of the sacrificial anodes? Any recommendations for procedures / documentation / literature?
Hi @aib Sorry for the delayed response here. I would be happy to answer your questions.
So we use two different types of sacrificial zinc annodes for the ROV and the larger platform that the ROV is tethered to. For the platform, I use pure Mil-spec zinc “pads” such as these from McMaster:
For the ROV, Blue Robotics installed the original zincs but I have noticed that they have not really decayed all that much so I am unsure if they are really doing anything. As we currently have the ROV up for just a quick tune-up before going back down for months or longer, I’m going to remove the annodes that are there and replacement them with ones that I’m fabricating from a pure zinc rod purchased also from McMaster. McMaster-Carr
Currently the ROV has a zinc attached to the bottom sides of the plastic frame and has wires with ring nuts running up to the various enclosures where they are connected to one of the M3 screws. These wires also run to each of the fathom lights where they are also connected by one of the screws on the back of the lights.
We didn’t calculate anything for the zincs, we just put what we thought was reasonable for the ROV and hoped they would last long enough. So far, so good.
You mention that the lumens are standard Bluerobotics. Have you had any problems at that depth? Are they the initial version lumens or the latest models? Do you think it would be convenient to add a thicker glass?
Hi Andres, We are using the most recent version of the lumens in the current deployment with wetlink penetrator. I would definitely recommend at the wetlink over any potted penetrator. We have been successful in the past with potted penetrators but they do have a self life and will eventually dry out and pull away from the metal shell. We recently pulled up our platform for a couple of weeks and redeployed again. While it was up, I did replace most of the lens’ on the lumens because they were damaged. They never failed but the fish on the bottom had given them quiet a beating. They were pretty scratched and some even had what appeared to be cracks. I’ve tried to protect them by 3D printing a shroud so that the fish cannot get their mouths over the whole light. I think the thickness of the lens isn’t a issue at least up to their rated depth. I also know that for a time BR had some defective lens’ that would easily crack. We were effected by this on one order when all our lights came with cracked lens’. BR quickly fixed this and shipped us new lens’.
The only other issue we have had was with the old version lumens on the ROV itself where previously they would dim depending on the amount of thrust. I think there was some issue in at least one of the thrusters that was causing some noise on the PWM line. That issue hasn’t come back since we replaced the thrusters with the newest version and new lights.
Hi, @Jhans, We installed ZeroTier on the RPi on the ROV. ZeroTier is free and is like a VPN so as long as the ROV has an internet connection, you can connect from anywhere using QgroundControl. ZeroTier also makes it easy to distribute the connection as well.
We have a custom charger board installed inside the 3" enclosure.
Aluminum anodes wouldn’t be much good with paired with aluminum enclosures nor the aluminum frame of our platform. Even though the cases are anodized, a scratch in the anodizing cause the enclosures not be protected.
Hi Stephen,
Do you have an email I can contact you with? I am with Louisiana State University’s iCore Lab and have some technical questions regarding this project.
Just as an update to this project, The ROV continues to function perfectly and has been continuously submerged at 900m in the Monterey Bay for almost 9-months (since May 5th 2022). Students from all over the world have had the opportunity to fly this ROV remotely including Australia, Japan, Vietnam, UK, Europe. We are currently working on the next iteration of this educational program that will includes new exciting features that allow for direct student involvement!
Check out our YouTube channel to see some of the amazing things we have discovered down there!
When doing similar long term ROV deployments (in fish pens, at vastly shallower depths) I’ve had success with these style zinc annodes - I drilled a hole and used a longer bolt per endcap to secure it directly to each flange.
@tony-white I would be interested to know how you prevent or mitigate bio fouling at the shallower depths during long term deployments? We may have other opportunities in the future to do this project in other locations that are shallower. Thanks!
In my case (aquaculture), we have visits from divers occurring regularly (for other fish husbandry and inspection tasks), so brief gloved hand-wipes of domes along with the presence of hundreds of thousands of (aggressive) fish keep things clean enough. For non-optical areas, a thick coating of vaseline mixed with chili-powder is a technique I learned for bio-foul prevention on sonar sensor heads, this seems to do well with enclosures and around endcaps/penetrators. Wrapping enclosures in vinyl (electrical tape) also can slow the rate of biofouling, and at least make cleanup vastly easier.
I’ve also seen LED UV lights of the appropriate wavelength have a dramatic (positive) affect on biofouling, but can consume significant power and more concerning, embrittle Acrylic. More testing required!
Can you give an detailed description of the whole zink anode system?
What materials are used to ensure the corrosion chain?
Are there copper wires that are connected between the aluminum casings and the zink anode?
And what types of screws/terminals?
Are looking into doing this on our equipent in a better way than today. We just have a zink anode connected directly to the enclosure, but those anodes gets quickly broken off due to the threads beeing eaten away.
Hi Rune,
I was trying to find a picture of the ROV that shows the zink but I can’t find anything. Honestly, I do not know how valuable the zink anodes are in my application though I can say that the enclosures have held up very well over their years of use. The zinks on the ROV itself does not seem to be decaying very fast whereas the zinks on my aluminum platform decay quiet a bit. I’m still using the same 4" enclosure as I have used since the start of this project five-ish years ago. We essentially try to use some pure zink connected to the enclosure using 10-12AWG copper electrical wire. The ring terminals were just standard from a terminal kit. Not sure of the material. Screws were just 316 stainless.
I think that Zink annodes directly connected to the enclosures would be better. You said they get broken off quickly due to threads getting corroded. Are you saying the internal aluminum threads get corroded quickly? That would make me think the zinks are not working well if the aluminum corrodes faster than the zinks.
Hi @hube268 -
Fighting biofouling is tough! For things like transducer heads, I learned the commono industry solution is to slather vaseline mixed with the spiciest chili powder you can find across the face of the transducer - this keeps barnacles and other tough growth from forming.
Copper is a biotoxin, and it can keep fouling at bay if positioned around a sensor - but this will affect some types of measurement! The most impressive solution I’ve seen is UV light of a particular ~440nm wavelength, which can keep a lot from growing even if exposed only intermittently. This has the risk of potentially making acrylic brittle!
@rune In my suggested approach, you only need Zinc pieces and longer bolts, no copper wire or ring terminals are necessary. Tef-gel is a great solution for preventing threads from corroding!