Corrosion Protection

[wlewis]

My new Freedom 225 has a one piece full platform/bracket make of aluminum. Unlike my old Gulfstream with a fiberglass platform mounted on top of an aluminum engine bracket, this one has an aluminum platform, welded to an aluminum engine bracket making it a single unit made of welded aluminum. Since my old Gulfstream had corrosion issues around the engine mounting bolts, I've become more aware of corrosion and want to protect and maintain the new boat's platform/bracket assembly. In fact, I've already found a small spot of tiny corrosion bubbles, about the size of a dime on the underside of the platform. I sanded them down and touched up the spot with the Grady supplied Imron touch up paint. Does anyone have any suggestions or ideas as to how to preserve and protect the platform/bracket from corrosion, particularly the underside, ie a wax, anti-corrosive protective sealant or spray?
Walter

 

[Wetcoast Noel]

Hello, I can help you with this one. I am not only a grady owner but also an aluminum welder, the corosion will never end so long as there is the tinyest fleck of exposed aluminum in Salt water , so you need to put on a sacrificial zink anode , I have an all aluminum pod on my grady also and put a generic 6" round zink designed for a sail boat rudder. one on each side of the pod. the salt will eat the zink and not the pod. Most zinks are actually the softest grade of aluminum and not really zink any more, but still called a zink.
I drilled a 1/8 th hole in the size of the pod where the zink will be below water level and used Sika flex in the stainless bolt hole. as long as the zink is in contact with the aluminum , it will be eaten and no damage will happen to your pod. a 6" round one cost me $12 and I will need to put on a new one next season, but its pretty cheap insurance to keep the corrossion from eating my pod.

Pick up any style of zink's at any marine parts store that sells parts for boats going in salt water.
:mrgreen:

 

[wlewis]

Noel,
Thanks for your input. My bracket already has a zinc on it, about a 3"-4" round one. Is that too small? Even though the boat is new, it was in dealer stock for 2 years before I bought it and it only has 13 hours on it, I'm just surprised it would corrode this soon. I've since checked it a bit closer and have found two more small blisters in the paint. I've sent an inquiry and pictures to Armstrong and await their response. Lacking any other suggestions, do you think it would help to periodically coat the bottom of the platform, particularly around the welds, with Corrosion X or BoShield? Would it be helpful to spray the inside of the bracket with same?
Walter

 

[wlewis]

Noel,
Thanks for your input. My bracket already has a zinc on it, about a 3"-4" round one. Is that too small? Even though the boat is new, it was in dealer stock for 2 years before I bought it and it only has 13 hours on it, I'm just surprised it would corrode this soon. I've since checked it a bit closer and have found two more small blisters in the paint. I've sent an inquiry and pictures to Armstrong and await their response. Lacking any other suggestions, do you think it would help to periodically coat the bottom of the platform, particularly around the welds, with Corrosion X or BoShield? Would it be helpful to spray the inside of the bracket with same?
Walter

 

[Wetcoast Noel]

I would put a zink on eash side of the pod, the blistering also might be from a fault in powder coating make sure your zink is physicaly attached to the boat, making contact , sounds odd, but people do put a stainless washer between them and then nullify the field and purpose. it has to be firly attached to the zink with no barriers to create the proper electode field . have a look, make sure there is nothing making a barrier like a washer or sticker or anything.
Noel

 

[wlewis]

Will check it, even though the zinc was mounted by Grady/Armstrong. I sure can't see how a second one on the other side would hurt. Thanks!

 

[wlewis]

Noel,
What is the significance of the sika flex? Isn't that a sealant, similar to 5200? If so, wouldn't that insulate the zinc from the aluminum and defeat the purpose of the adding the zinc?
Walter

 

[Wetcoast Noel]

Hi, the Sika flex is a plyable sealant in a tube, not sure what 5200 is, probably similar. its purpose in this case to so when you drill a hole in a perfectly good pod to attach the zink with a stainless nut/bolt, sea water will not work its way into that perfectly good pod and flood it, taking away your extra floatation the pod gives and your not paying to push 800 extra pounds of seawater..... if you attach the zink properly, it will have a zink to aluminum flush mount where it connects on much of its back surface creating the electrical barrier of the softer metal for the sea water to eat and not eat your pod.
when I put on my zinks onto my Grady, I sand the area under the old zink ( just scuff it up) to make some clean surface points, and I put a few drops of dieelectrical grease under the body of the new zink to ensure a connection .

On another note. many of us with pods have a water drain hole in the bottom. DO NOT ever ever ever ever use a copper or any plug that could contain copper into anything made of aluminum spend the $5 buy a stainless plug. Copper eats Aluminum, don't believe me ? toss a penny on a peice of aluminum and watch it start to etch it by the next day. and if you paint your pod, make sure there is no copper in the pain to fight barnacles, the copper based paint will disolve your pod over a few weeks/ months

A good friend of mine had his aluminum Cat cleaned up and paid a shipyard to put the antifouling paint on it, within 2 months he was sinking with pin holes, cost the ship yard over 200k for a new cat bottom on his boat after the lawsuit...

 

[wlewis]

Great info Noel.5200 is a 3M sealant that is as close to permanent as you can get. It probably would not be recommended for this application as it's too permanent. If used, you might never remove the old zinc. My bracket does have a plastic drain plug on the bottom. My brother has an Striker, which as with all Strikers, is made out of aluminum. He tells me if you place too many zincs on aluminum, it will eat the paint. I'm still waiting to hear from Armstrong.