Trim tab pitting corroding ?

Blueone

Blueone

Well-Known Member
SILVER Sponsor
Jan 24, 2007
13,777
Lake Erie, Ohio
Boat Info
2004 420 Sundancer
Engines
Cummins 6CTA 450's
I have had this occurring for a couple of years. The boat is in fresh water only. I am getting this pitting just on the tabs, there are no issues anywhere else. I thought it might be stray current from the marina ..but 2 seasons ago I moved to another marina. Last winter I just bottom painted the tabs again... in the new marina I get the same result.

Also my magnesium anodes are deteriorating quickly in my opinion. You can see the anodes on the tabs and a fuzzy pic in the center... both are 2 years old

What do you think is causing the pitting on the tabs ?

C21B1D25-A5AB-4160-A3DC-AFC0E4B23856.jpeg


FD3AE57A-4206-49F7-B29E-5830714A50FD.jpeg
 
BoatZincs sells a tool you can use to measure stray current in the water.
In the meantime, make sure your bonding system (green wires) and all the connectors on it are in good shape.
 
What type of bottom paint are you using? Does it have any metals (copper) in it? If so, that could be causing the issue (dissimilar metals = corrosion).

I'd rather see anodes wear away a little faster than too slow. Too slow would not be providing enough protection. Actually, in the picture, the tab anode doesn't really look worn - just covered in growth. You might try switching to an Al anode.
 
Lazy Daze said:
What type of bottom paint are you using? Does it have any metals (copper) in it? If so, that could be causing the issue (dissimilar metals = corrosion).

I'd rather see anodes wear away a little faster than too slow. Too slow would not be providing enough protection. Actually, in the picture, the tab anode doesn't really look worn - just covered in growth. You might try switching to an Al anode.
Click to expand...
It’s petite ...water based basic stuff ...
The pic of the transom anode is bad but it has deep pits in it...so does the tab anode...
the pitting is everywhere on the tab and both tabs are the same
 
The stainless of the tabs should be the more noble of the metals in the water. As such, the electrons should be flowing from the magnesium or other metals. The tabs should not be giving up anything. Are your tabs being dissolved or is something forming on the surface?
 
DWABoat said:
The stainless of the tabs should be the more noble of the metals in the water. As such, the electrons should be flowing from the magnesium or other metals. The tabs should not be giving up anything. Are your tabs being dissolved or is something forming on the surface?
Click to expand...
I guess it’s not pitting necessarily...it’s creating some corrosion or something on the surface that pops the paint off in the small circles
 
Sounds like a paint issue.
Have you changed to a new paint lately?
Maybe the surface prep wasn’t done properly for last paint job?

I have heard before that if your corrosion protection system is too active, blistering paint could result.

Sorry I can’t be of any help here.

Are you experiencing any corrosion, meaning dissolving away, of any submerged metal components?
 
DWABoat said:
Are you experiencing any corrosion, meaning dissolving away, of any submerged metal components?
Click to expand...
No everything else coming out of the water looks exactly the same as it went in ...for 4 years now.

I was thinking of just stripping them...never liked the painted look
 
Blueone said:
It’s petite ...water based basic stuff ...
The pic of the transom anode is bad but it has deep pits in it...so does the tab anode...
the pitting is everywhere on the tab and both tabs are the same
Click to expand...
But... even the water-based stuff can contain metals - it depends on which version of the paint was used. Do you happen to still have the can - or recall which version?

EDIT: Take a look at this: http://www.pettitpaint.com/products/antifouling-bottom-paint/hydrocoat/
 
Lazy Daze said:
But... even the water-based stuff can contain metals - it depends on which version of the paint was used. Do you happen to still have the can - or recall which version?

EDIT: Take a look at this: http://www.pettitpaint.com/products/antifouling-bottom-paint/hydrocoat/
Click to expand...
It’s hydrocoat I have been using .... it looks like they want Barnacle barrier first....so your right....could be the paint. But a bit odd just little spots.
I think I will take them off and strip them..

4E6F9746-EC5E-429B-BCF8-9D870655FD80.jpeg
 
A old friend who has been repairing boats for 40 years at Fort Washington told me that the single worst thing you can do to trim tabs is paint them with bottom paint. Effectively the bottom paint contains copper or other metals and effectively you are creating a battery like reaction in the trim tabs causing the pitting that you are seeing.

If you are going to paint them which is unnecessary in fresh water......use Trilux which is used on outboards and stern drives. The downside is you need to get the old paint off the tabs.
 
PlayDate said:
A old friend who has been repairing boats for 40 years at Fort Washington told me that the single worst thing you can do to trim tabs is paint them with bottom paint. Effectively the bottom paint contains copper or other metals and effectively you are creating a battery like reaction in the trim tabs causing the pitting that you are seeing.

If you are going to paint them which is unnecessary in fresh water......use Trilux which is used on outboards and stern drives. The downside is you need to get the old paint off the tabs.
Click to expand...
Thanks ..I bought the boat like this and wondered why they were painted... I will remove them clean them up and rebed
 
I don’t know the cause or origin but that looks like electrolysis.

I’ve had quite an experience w electrolysis such that I hate wet slipping.
 
Trim tab porn :) They are now naked

I took them off and took them to the shop and glass beaded them.... it took a while as glass bead is more for surface finish then stripping old paint... but they came up nice.... so last project done under the rub rail :) Time to splash.... soon as it gets above 50 deg... what the heck?

before:
7A8FE3CD-FDA6-4ECD-BBC0-3DE27352E376.jpeg


Under water bling !!

3B61A79A-26EC-4264-8AB1-4E0418EBFB45.jpeg

F78CD418-7D68-4A2D-B874-772B46D19C17.jpeg
 
Last edited:
FYI - At the Defender warehouse sale a few years back the Pettit guy told me to try prop coat on my tabs. It worked well keeping barnicles off. Later I read that rustoleum cold galvanized paint has the same properties for about 6 bucks a can so I tired it a few years back. I've had success keeping growth and pitting at bay on my boat.

I tried the naked approach with no luck. Then I tried pettite process of etching and hard paint to no avail. Finally good luck with the method above.

I realize you are in fresh water so I'm not sure the results would be the same-just sharing.
 
It appears there was paint under the anodes and insulating the anode from the tab metal; most likely the root of the issue. SR doesn't bond the tabs to the boat's bonding system consequently the electrical bonding of the anode to the tab is pretty important.
Also, if your other anodes are going away rapidly I suspect you have an issue with the electrical system on the boat and leaking current into the water; this will have an adverse affect on the tabs as well.
 
ttmott said:
It appears there was paint under the anodes and insulating the anode from the tab metal; most likely the root of the issue. SR doesn't bond the tabs to the boat's bonding system consequently the electrical bonding of the anode to the tab is pretty important.
Also, if your other anodes are going away rapidly I suspect you have an issue with the electrical system on the boat and leaking current into the water; this will have an adverse affect on the tabs as well.
Click to expand...
There was not paint under the anodes

How would you go about finding the cause of leaking current if that was the case?
 
You must log in or register to reply here.

Forum statistics

Threads
113,101
Messages
1,425,946
Members
61,018
Latest member
IslandGirls1020
Back
Top