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My friend and customer bought his boat in Florida and then sailed it to Lake Superior. The salt water did a job to some of the aluminum components of the swim platform. I machined a couple of parts for the new swim platform, but I couldnt help Ray with the main fabrication because it was too thick for my Dynasty 200 DX welder. The components of the swim platform were powder coated. Some areas are still in pristine shape but the salt water must have got through or around the powder coating and badly corroded other areas. The first picture shows the swim platform before it was cleaned up.1. Original swim platform mechanism
The next picture shows the corrosion on the bearing journals of the main fabrication link of the swim platform.2. Heavy corrosion of the bearing journals
Picture 3 shows a close up of two of the journals of the main fabrication.3. Close up of the journal corrosion.
Picture 4 shows the new swim platform.4. New swim platform
Picture 5 is a close up view of the new journals of the new swim platform.5. New Journals
Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE 31 MP & Lincoln 210 MP
Reply:The last picture shows the swim platform mounted on the boat.6. New swim platform mounted on boat
Here is a link to another post from Tarry99 regarding corrosion and salt water.https://forum.millerwelds.com/forum/...991#post614991-DonLast edited by Don52; 05-21-2021 at 01:18 PM.Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE 31 MP & Lincoln 210 MP
Reply:The majority of the corrosion is so localized it makes me wonder if there was some electrolysis involved!
Reply:Absolutely there was. My guess is he has a problem with the sacrificial anode system on that boat. Probably (just a guess) the swim platform is not electrically connected to the sacrificial anodes (zincs) at all. That is usually the number one cause of galvanic corrosion in a boat equipped with zincs. The part being protected has to be in the same circuit as the zinc anodes.
Reply:I know very little about boats(except I don't want one!
) but that was going to be my wild *** guess!
Reply:As far as I know, you are supposed to throw your anodes out at the swim board since that's where the electrolysis happens?Sent from my SM-G960U using Tapatalk
Reply:It doesn't matter where the anodes are as long as they are below water and connected (grounded?) to all the parts needing protection.
Reply:
Originally Posted by Louie1961
Absolutely there was. My guess is he has a problem with the sacrificial anode system on that boat. Probably (just a guess) the swim platform is not electrically connected to the sacrificial anodes (zincs) at all. That is usually the number one cause of galvanic corrosion in a boat equipped with zincs. The part being protected has to be in the same circuit as the zinc anodes.
Reply:
Originally Posted by Louie1961
It doesn't matter where the anodes are as long as they are below water and connected (grounded?) to all the parts needing protection.
Reply:Bonded..cool. in a boat it's not so much difference in potential as dissimilar metals in salt water act as a battery. If you connect something like a zinc to those two dissimilar metals, the zinc will give up it's electrons first, thereby saving the other metals.
Reply:
Originally Posted by Louie1961
Bonded..cool. in a boat it's not so much difference in potential as dissimilar metals in salt water act as a battery. If you connect something like a zinc to those two dissimilar metals, the zinc will give up it's electrons first, thereby saving the other metals.
Reply:Ray confirmed that there he didnt find an anode on the old platform. This picture shows the shaft in the corroded journal. You can also see the plastic bearings.
-DonSmith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE 31 MP & Lincoln 210 MP
Reply:I did a little research about anodes. It turns out that for optimal protection you need different materials for different water. Zinc Alloy Anodes = Salt water only * Not recommended for use in fresh water * Alloy is manufactured to meet or exceed US Military Specification (MIL-A-18001K) Aluminum Alloy Anodes = Salt or Brackish water * Not recommended for use in fresh water * Proven to last longer than zinc due to increased capacity * Alloy is manufactured to meet or exceed US Military Specification (MIL-A-24779(SH)) Magnesium Alloy Anodes = Fresh water only * Not recommended for use in salt or brackish water * The only alloy proven to protect your boat in fresh waterHere is a link to my reference.https://www.defender.com/html/zincs_info.html-DonLast edited by Don52; 05-22-2021 at 01:14 AM.Smith Oxyacetylene TorchMiller Dynasty 200DXLincoln SP-250 MIG WelderClausing/Coldchester 15" Lathe16" DuAll Saw15" Drill Press7" x 9" Swivel Head Horizontal Band Saw20 Ton Arbor Press BridgeportLincoln LE 31 MP & Lincoln 210 MP
Reply:I would be leery of using an aluminum alloy sacrificial anode on an aluminum alloy swim platform. I would probably stick to zincs. Corrosion in fresh water is much slower/less aggressive in my experience.
Reply:
Originally Posted by PDXsparky
Not "grounded", the correct term would be bonded. It's like an in-ground swimming pool. All the metal parts; the rebar, the hand rail sockets in the deck, the wet niche light housing, the pump motor, and any metal fencing within a minimum distance are mechanically bonded together with #8 AWG solid copper wire. That keeps the potential energy plane equal, like birds on energized power lines. If the metallic pool parts weren't bonded, then there could be a difference in potential energy. That's how you get shocked.
Reply:
Originally Posted by Country Metals
As far as I know, you are supposed to throw your anodes out at the swim board since that's where the electrolysis happens?Sent from my SM-G960U using Tapatalk
Reply:
Originally Posted by Willie B
Since you brought up pool bonding. Some components must also be grounded. If a pool's equipment room is at one end, but pool cover, niche lights, and the only point to bond the aluminum coping are all on the other end, is it acceptable to use the bare copper ground conductor for grounding? I'm refitting a 1990 indoor pool. Everything is PVC conduits buried in concrete. Supply feeder uses a #8 solid for grounding, it'd be convenient to share it for bonding. Almost no bonding was done in 1990. There is no bonding grid under the pool.
Reply:
Originally Posted by Willie B
Since you brought up pool bonding. Some components must also be grounded. If a pool's equipment room is at one end, but pool cover, niche lights, and the only point to bond the aluminum coping are all on the other end, is it acceptable to use the bare copper ground conductor for grounding? I'm refitting a 1990 indoor pool. Everything is PVC conduits buried in concrete. Supply feeder uses a #8 solid for grounding, it'd be convenient to share it for bonding. Almost no bonding was done in 1990. There is no bonding grid under the pool.
Reply:
Originally Posted by danielplace
680.5 GFCI’s may be either circuit breakers or receptacle type.680.8 Max. cord length for a pump motor is 3’ except for storable pools.680.9 Overhead wire clearance is min. 10’ horizontal from the pool wall.680.11 Underground wiring shall comply with 680.11. Wiring shall not be allowed under a pool unless it’s to supply pool equipment.680.13 A means of disconnection such as a switch or plug must be within sight of the equipment served.680.14(B) Wiring methods shall be in Rigid conduit, Intermediate conduit,PVC conduit, RTRC conduit or listed MC cable where installed in a Corrosive Environment. Flex is allowed at the pump motor.680.22(A)(1) At least one general purpose receptacle from 6’ to 20’ away is required.680.22(A)(2) Receptacles for pump motors minimum 6’ from the pool wall must be GFCI protected.680.22(A)(3) Other Receptacles shall be at least 6’from the pool wall and GFCI protected.680.26(B)(2) Perimeter bonding is required for permanent pools. A minimum #8 AWG copper wire (ground ring) must be installed around the pool 4” to 6” below grade, 18” to 24” from the pool and connect to the pump motor, heater and the pool water bonding.680.26(B) 4 Point bonding is not required to the vertical uprights of pools with Vinyl Liners as it is considered a nonconductive material.“For nonconductive pool shells, bonding at 4 points shall not be required”680.26(C) The pool water must be bonded to at least 9 sq” of metal. This may be accomplished by:1. Bonding to a pool water heater that has metallic components.2. Installing a metal pipe nipple in the water circulation system so a ground strap may be attached to it.3. Other approved methods.
Reply:Getting back to the original swim platform corrosion... That's horrible, I assume it's not marine grade alloy?my first thought was galvanic corrosion also (preferential corrosion, if you will) causing the pivot point to disappear first - if there were any dissimilar metals in that pivot point area. Since there were plastic bearings and the shaft was alloy, we can't blame it on the pivot shaft. Possibly different grades, but again, the plastic bearings would prevent galvanic.My next thought would be localised corrosion in the area of highest stress (the pivot point). It seems that few people know that you always get more corrosion in the areas of highest stress concentration.Absolutely, if the platform had had zinc anodes, it would have had a degree of protection. Or if the platform was acting as the only anode on the boat, then that's a major problem right there.Last edited by Munkul; 05-24-2021 at 03:28 AM.Murphy's Golden Rule: Whoever has the gold, makes the rules. |
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发表于 2021-9-1 23:17:56