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Help Insulating stainless screw from powder coated surface


Shallowminded6

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So, I am replacing my splashwell cap. I am trying to figure out the best way to keep the freshly powder coated surface from getting messed up from installing the screws and keeping it from starting electrolisis. I understand it is an up hill battle I will lose eventually. Just trying to extend the life as long as possible since it is a PIA to replace. So far, I have come up with plasti dipping screw heads. The metal is countersunk (powdercoated), and the screws are #10-#12 countersunk stainless screws. So I didnt think washers would work?  Any suggestions?? Am I looking too far into this and just install and forget about it?

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22 hours ago, Shallowminded6 said:

So, I am replacing my splashwell cap. I am trying to figure out the best way to keep the freshly powder coated surface from getting messed up from installing the screws and keeping it from starting electrolisis. I understand it is an up hill battle I will lose eventually. Just trying to extend the life as long as possible since it is a PIA to replace. So far, I have come up with plasti dipping screw heads. The metal is countersunk (powdercoated), and the screws are #10-#12 countersunk stainless screws. So I didnt think washers would work?  Any suggestions?? Am I looking too far into this and just install and forget about it?

I guess you could connect one of the stainless screws on the surface of the aluminum structure to the sacrificial zinc anode on your outboard motor, with a thin braided stainless cable.  In theory, that would protect against galvanic corrosion between the aluminum and stainless.  However, it would also ground your aluminum structure with connection to the water, so I wouldn't advise holding on to it in a lightning storm.

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51 minutes ago, geeviam said:

I guess you could connect one of the stainless screws on the surface of the aluminum structure to the sacrificial zinc anode on your outboard motor, with a thin braided stainless cable.  In theory, that would protect against galvanic corrosion between the aluminum and stainless.  However, it would also ground your aluminum structure with connection to the water, so I wouldn't advise holding on to it in a lightning storm.

Would you have to do a ground wire to each screw? Or would it transfer thru alluminum to the small cable? Cant use flat washer as it is countersunk. Plastic ones just break when tightened. 

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1 hour ago, Shallowminded6 said:

Would you have to do a ground wire to each screw? Or would it transfer thru alluminum to the small cable? Cant use flat washer as it is countersunk. Plastic ones just break when tightened. 

Just one screw on the structure near the motor, to make a connection for the current to flow to the zinc anode.  The wire should have metal-to-metal contact with the embedded stainless screw - not strapped to powdercoat, since the powdercoat is an insulator.

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On 3/8/2020 at 8:22 AM, geeviam said:

I guess you could connect one of the stainless screws on the surface of the aluminum structure to the sacrificial zinc anode on your outboard motor, with a thin braided stainless cable.  In theory, that would protect against galvanic corrosion between the aluminum and stainless.  However, it would also ground your aluminum structure with connection to the water, so I wouldn't advise holding on to it in a lightning storm.

so fun dichotomy...some sailors swear by clipping a wire to their rigging and dragging it in the water during a lightning storm to divert the lightning overboard instead of through their boat...go figure.

I'm guessing that not enough people survive those lightning strikes to tell us which way is better. ;-).

 

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