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Pitting


CLIVE58

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there might just be a theoretical difference in the metals and a risk of electrolysis but then how else can you join steel together. I reckon its OK to fill pits with epoxy filler, whatever keeps the water away from the steel.

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54 minutes ago, NB Esk said:

Yes, it's okay, I'll be doing just that in a week or two.....

 

 

Can you give me any pointers, like what sort of welder and would you use a grinder with a wire brush head please. 

 

 

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3 hours ago, Bee said:

there might just be a theoretical difference in the metals and a risk of electrolysis but then how else can you join steel together. I reckon its OK to fill pits with epoxy filler, whatever keeps the water away from the steel.

Welding is the only "proper" way - any sort of filler runs the risk of water being trapped where it hasn't truly bonded to the steel which in a "pit" is even harder to achieve without trapping air and a failed bond

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4 hours ago, CLIVE58 said:

Can you give me any pointers, like what sort of welder and would you use a grinder with a wire brush head please. 

 

 

Sure, I only use stick welding for boat stuff.  Mig is good but, in my opinion, not for outdoor use.  Stick welding gives good penetration and is tolerant of difficult preparation (depending on type of electrodes used).

Rotary wire brush on an angle grinder should sort the preparation.

Good luck with it....

 

 

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4 hours ago, CLIVE58 said:

Can you give me any pointers, like what sort of welder and would you use a grinder with a wire brush head please. 

 

 

If I was doing it I would wire brush then clean the surface with an angle grinder using an abrasive pad or not too course flap wheel, then (depending on how rusty) clean the pit with a counter sunk bit, but obviously not making the pit significantly deeper.  Then weld up with a stick welder.

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4 hours ago, Bee said:

there might just be a theoretical difference in the metals and a risk of electrolysis but then how else can you join steel together. I reckon its OK to fill pits with epoxy filler, whatever keeps the water away from the steel.

Good point and quite right, I've often seen perfectly good steelwork alongside deteriorated weld metals. 

 

 

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My hull suffered fairly serious pitting in it's first five years (I was still fitting it out). Consequently I did a fair amount 'pit' welding over the next few years using both MIG and stick. (note, I am NOT a welder) I found the stick welder easier and I would strongly recommend a solar mask.

You need to be systematic  as it's easy to get confused as to which area you have inspected / welded. A piece of chalk is very useful. A low stool is advisable as it's back breaking after a while. I used 2 small grinders , one with a wire wheel to clear out the pit and one with a grinding disc to grind down the weld. I had already insulated and lined the hull sides but fortunately had used rockwool so fire wasn't a concern or an issue. Be prepared to repeat the process the next time you have the boat out because you WILL miss some pits. I've had no issues since with dissimilar metals.

 

Good luck :giggles:

 

Frank

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22 hours ago, Chewbacka said:

If I was doing it I would wire brush then clean the surface with an angle grinder using an abrasive pad or not too course flap wheel, then (depending on how rusty) clean the pit with a counter sunk bit, but obviously not making the pit significantly deeper.  Then weld up with a stick welder.

Or just use a wire wheel to get the the bottom of the pits. I spent several months doing that on the badly corroded insides of two c1890s 90ft rivetted steel steam boats. We couldn't use needle guns due to the danger of going through the steel, but with wire wheels on an angle grinder and a chipping hammer for the really bad rust scale you can get it very clean. There's no truth that paint won't stick to the "polished" steel - in fact on a microscopic level it's not really polished at all, but you can always give it a key if you're concerned.

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