Massive Corrosion Raw Water Strainer

[silverp40]

This 1" Perko raw water strainer has suffered from massive corrosion. Hard to tell why, but owner maintains neighbor's large powerboat caused it.

Could probably be cleaned somewhat with acid but it does not seem too safe...

Any opinions??

Cheers!

[SaltyBard]

Is the boat in the water? I'd worry about thru-hulls!

[steamgoat]

How would the neigbours boat be responsible, it looks like rubber in and out so isolated,looks like leaking, be more interesting to see the inside. IF the boat next door is responsible for this, I hate to think what other equipment is like.

[stillbuilding]

How would the neighbour's boat cause corrosion on the exterior I wonder?

Get a new one of course but seems strange for a bronze item unless it degraded over several years.

[Maine Sail]

Originally Posted by silverp40

This 1" Perko raw water strainer has suffered from massive corrosion. Hard to tell why, but owner maintains neighbor's large powerboat caused it.

Could probably be cleaned somewhat with acid but it does not seem too safe...

Any opinions??

Cheers!

Take it apart and have the parts bead blasted or use a wire wheel on a bench grinder. You'll likely find it in good shape. The plastic can be cleaned and polished clear again and a new gasket set ordered.

[Nor'Sea 27]

What is the white wire (photo left of your hand?) Are the in and out elbows bronze, brass, or can you tell? What material are the hose barbs that are screwed into these two elbows?

Obviously, if this type corrosion is not found elsewhere in your boat's underwater metals then it is unlikely this is a neighbor issue. Neighbor involvement not likely if the strainer is not bonded and/or you have galvanic isolation in your shore power.

In all cases it is way easy to measure your DC hull potential and the strainer potential too thus to to rule out neighbor involvement. Also this will show whether you have DC stray current on your own boat -- which is more likely if the damage occurred suddenly.

Bottom line - you might clean up but you cannot consider reuse until after clean up and verify the unit is worth putting back - but no brass alloys allowed in the fittings here - not ever. You need to know if there is enough metal left for service and no stray DC current flowing in your boat.

Based on this photo I would not reinstall - but either way you must make sure whatever goes back in is all bronze components.

Charles

[Cheechako]

is it really corroded.... or just green... cant tell..... green in no problem. If it's actually corroded away I would probably try bonding the new one. If it's bonded... I would unbond it. I doubt if a nearby boat or AC power caused it unless it's bonded to something..... it appears like it's been seeping for a long time.

[foggysail]

I agree with Mainsail, clean it up!

I have a different thought on why this thing turned green. HOW CLOSE IT IT TO THE BATTERIES??? If this was galvanic corrosion, I would expect the corrosion to be be INSIDE the filter. Your pictures show the device's exterior covered with what looks to be the result of acid fumes. Again my thought is this is too close the batteries and the outgasing from them is responsible. But please keep us up to date with your neighbor's progress.

Foggy

[Rhapsody-NS27]

to me it looks like it just disintegrated. Looks like an ugly mess.

[Watercolor]

Unless there's something else we can't see, the only metal contact to the tru-hull and the strainer would be the metal reinforcement in the hose. The strainer is mounted on a bulkhead is assume.

1. What do the seacocks look like? Especially the one connecting to the strainer?

2. Is there anything that can be dripping from above the strainer?

3. Take the strainer out if possible and clean it up, see if you can ascertain how much corrosion there really is. It may give you some clues. I have the feeling Steamgoat might be on to something.

4. What material are the street elbows and barbed fittings made of?

5. Are there any wires that could be touching the strainer?

6. The last thought is the SeaFrost condenser unit. Check the condition of the zinc in the unit along with the coil. I just remembered that we had to change out the zinc once a year.

Good luck!

[Delfin]

I know that some folks are fond of putting hot tub bromide tablets into their raw water strainer to clean out the system. Since the bromide reacts with salt water to produce highly corrosive bromine gas I suppose this might be a possibility.

[silverp40]

This occured over 2-3 years, we were not here at the time and the power boat has left. He was saying that his zincs would go within 1 month or so. Hence, probably stray current, maybe bad grounding on the shore power?

His bonding cables, just visible on the bottom of the photo, were completely corroded, just fell out of their terminals.

Entire unit is a Perko, I am pretty sure it is bronze, hose fitttings probably same.

The electrical grounding on his boat was not good so I put a good grounding on it to eliminate that possibility.

No dripping from above, inside strainer basket looks fine.

Cleaning it up is a bit of a big deal, the corrosion is hard as rock It is hard to even chip any! I was thinking of a soak in vinegar or maybe even muriatic acid but I have a feeling that it might damage it further...

It is close to the batteries but they are maintenance free and no other signs of outgassing.

No bromide tablets in this one...

[Maine Sail]

Originally Posted by silverp40

This occured over 2-3 years, we were not here at the time and the power boat has left. He was saying that his zincs would go within 1 month or so. Hence, probably stray current, maybe bad grounding on the shore power?

His bonding cables, just visible on the bottom of the photo, were completely corroded, just fell out of their terminals.

Entire unit is a Perko, I am pretty sure it is bronze, hose fitttings probably same.

The electrical grounding on his boat was not good so I put a good grounding on it to eliminate that possibility.

No dripping from above, inside strainer basket looks fine.

Cleaning it up is a bit of a big deal, the corrosion is hard as rock It is hard to even chip any! I was thinking of a soak in vinegar or maybe even muriatic acid but I have a feeling that it might damage it further...

It is close to the batteries but they are maintenance free and no other signs of outgassing.

No bromide tablets in this one...

It looks to me like a weeping clean out gasket could have caused that....

These are expensive strainers and they will very often clean up like new with the right tools.

I happen to be in the shop this morning and pulled a used one out of a box. Certainly not the worst patina I have seen but it shows what you can do in as little as 5 minutes with a bench grinder and wire wheel. I have a had some realty nasty ones, that look like yours, clean up like new with no signs of dezincification or corrosion. Perko uses a high quality bronze on these...

Including disassembly this took me less than 5 minutes. Took longer to upload the photo..


Here's what they look like when ready to go back together.


And ready to be re-installed for many more years of service.



P.S. If you don't want yours, I will be glad to pay for shipping it to me........

OK back to work...

[silverp40]

Thanks Main Sail ,just thought that after a lot of grinding work, corrosion of the components would deem the unit useless.

I will definitely tell him and give it a try though....

[rwidman]

It appears to me that the corrosion is on the outside of the strainer. It cannot be blamed on another boat. There's either salt water leaking somewhere or as someone mentioned, battery fumes. I had a strainer that did that (not so severe) and it turned out the plastic cover was cracked and seawater was seeping through the crack and keeping the bronze wet.

I don't know how a grinder could get the corrosion off in the nooks and crannies. I would think of sandblasting if possible.