Quintrex fuel tank corrosion

Hi All,

 

Due to having some spare time on my hands (like a lot of people at the moment) I decided it was the perfect time to do some work on my boat. It started with a fuel sender unit that wasn't reading, after removing that and noticing the state of the fuel (and water) inside I decided to go one step further and remove the tank for cleaning.

 

What i didn't expect was to punch through the bottom of the tank with my silicone tube I was using to syphon the last bit of fuel out on my work bench, see pics below.

 

My question and concern is the type of corrosion. It appears to have developed externally and is very localised, I am concerned about electrolysis. The effected section is the bottom of the tank and it is not in contact with anything as it hangs from brackets above.

 

Any advice on repair (explosion hazards understood and accounted for), replace, what to do stop it happening, how to check for stray currents etc. etc. would be much appreciated.

 

I have also put up some pics of the pitting inside the hull, nothing too deep at this stage.

 

Trav

Image Upload: 

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Date Joined: 16/05/09

Condensation or water sitting

Wed, 2020-04-15 15:26

Condensation or water sitting in the hull will do that. New tank me thinks.

sstevee's picture

Posts: 466

Date Joined: 15/11/11

Was the fuel sender in one

Wed, 2020-04-15 18:42

Was the fuel sender in one piece when it came out of the tank? If the arm or any part of it has corroded and fallen off it would have then sat in the water in the bottom of the tank and continued to corrode/eat out the aluminium. The other thing would be to ensure that no electrical items on the boat are earthed to the hull.

Also, when you do sort it out make sure the fuel sender is electrically isolated by design, they may all be but I'm not sure.

As for the water in the tank, not sure where the breathers are on yours but on my old quinny they were mid hull and very exposed to sea spray. I ended up replacing the lines and making sure that they looped upwards under the gunnel before coming back down below the line of the breather to make sure sea spray didnt end up in the tank.

Sucks to have happened but better discovering it on your terms rather than run out fuel one day coz its all in your hull!

Steve

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Date Joined: 19/02/15

Fuel sender was in one piece

Wed, 2020-04-15 21:17

Fuel sender was in one piece but it was a cheap one by the looks, couldn't see anything missing anyway. I have ordered a Wema from whitworths, I think they are good ones.

I'm a bit paranoid about the electrolysis so I will do some checking on earthing and stray currents. It's all a bit of a mess under the dash to.

The breathers are the rear facing ones with the cowling around them, towards the stern on both sides.

Yeah, i agree. I'm not too upset about it, kind of glad I found it.

Thanks for your help Steve.

little johnny's picture

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Of memory

Wed, 2020-04-15 19:09

Not sure what year Quintrex it was . They used a glue on carpet once washed went into hull that caused massive corrosion problems . Guy passed away now . Good old ken . Someone on site will know . If not that . I would check your earth for electronics . Some people earth out to dash . ( underneath) bad move ) seen it many times.

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Date Joined: 19/02/15

Thanks for the reply, I will

Wed, 2020-04-15 21:19

Thanks for the reply, I will look into it.

Mine is about a 2004 I think.

Jackalchub's picture

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 The structural beam pic is a

Wed, 2020-04-15 20:16

 The structural beam pic is a bit more drastic than the one you sent me. check your neutrals as mentioned.. call me for any q's

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Date Joined: 19/02/15

Nothing too deep in the hull

Wed, 2020-04-15 21:21

Nothing too deep in the hull that I can see thankfully. I just can't tell (or don't know) the difference between salt pitting and electrolysis though. Just have to do some checking. 

Faulkner Family's picture

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Date Joined: 11/03/08

 Rather than repair that one

Wed, 2020-04-15 20:30

 Rather than repair that one hav e a look at the 70 ltr plastic ones. Got one in my boat . Depends of the space you have to put one in

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RUSS and SANDY. A family that fishes together stays together

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Date Joined: 19/02/15

 Will do, thanks. Although

Wed, 2020-04-15 21:23

 Will do, thanks. Although this ones about 100L from my calcs and fills the space quite nicely.

chevaps's picture

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Date Joined: 04/01/13

Trav. There appears to be

Sat, 2020-04-18 01:39

Trav.

 

There appears to be alot of white spots on the hull.  I hope these are just water stains (which are benign) with the odd coincidental area with some pitting.

 

For now i would ignore the whole "stray currents", "electrolysis", and ensuring no electrical equipment is "earthed" to the hull line of thinking - given this is in a trailer boat, it's unlikely to be the cause of your problems and will just send you down a rabbit hole and create an unncessary sense of panic or paranoia.  There are a heap of other more likley mechanisms to consider, such as:

i) a "poorer quality" 5083 aluminum alloy, with compositions that make it less resistant to seawater - there's not much you can do about this unfortunately.

ii) localised dirt or debris causing a localised chemical reaction with aluminium leading to galvanic corrosion, which is intesified in the presence of water, and magnified further in the presence of salt water - quite likely in your case given the extent of corrosion on your fuel tank.  Note, the offending particles may have initiated the corrision, but have since been washed away.

iii) pooling of water in the bilge for extended periods leading to crevice corrosion.

iii) washing aluminium with an alkaline solution (many degreasers and bilge wash concentrates are storng alkalines), especially if the aluminium oxide layer is already compromised - possible, but you know the cleaning history of your boat the best.

 

I would focus of thoroughly cleaning the hull below deck to ascertain how bad the pitting is.  With any luck, you will only find a few problematic areas which you can bring to the attention of a boat builder who will advise if repair is possible.  Also, see if there are any areas where water will pool (due to lack of, or blocked, mouse holes), and try to address these if possible.

Regarding the tank, as other have already suggested, look at a replacement.

 

Hope you can get this resolved.

 

Tom.

 

 

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Date Joined: 19/02/15

Thanks Tom, Great,

Sun, 2020-04-19 08:04

Thanks Tom,

 

Great, constructive reply and good advice.

 

The hull is in reasonable condition, none of the pitting is at a depth to be concerned about just yet. That's how i want it to stay though and hence my concern for the long term.

 

It is a 16 year old boat and I have had it less than a year, so not sure on its history. That's one of the reasons I decided to pull the tank out, now I can clean it up and be sure of what's lying under the floor.

 

I would say point II or III is the main culprit, poor cleaning with either pooled water for extended periods or debris. On advice of a boat builder, I will clean it down with a light sand and apply some lanolin oil.

 

Tank is all repaired now (cut out and re-plated the bottom) and I will put it back in during the week.

 

Thanks again for your reply, it's good to hear from others with more marine experience than me.

 

Cheers,

Trav

 

 

Jackalchub's picture

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 What he said ^ 

Sat, 2020-04-18 04:53

 What he said ^ 

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Date Joined: 19/02/15

Cheers Mate

Sun, 2020-04-19 08:05

 

sea-kem's picture

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 Sorry to say it mate you

Sat, 2020-04-18 07:42

 Sorry to say it mate you just  haven't been cleaning your boat good enough. I've got a similar hull and stuff the hose up the front after every few trips and flush out. Once a year the floor comes out and a full clean. 

The tank is cactus

Like above you need a boat fabricator to have a good look at it and give you some advice on how bad the pitting is. I had a bloke come to my workshop once wanting some patching on a dinghy he'd just bought. The pitting was so bad and covered nearly the entire base of the hull I told him to scrap it, and that was the reason he'd gotten a 'bargain'.

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Date Joined: 19/02/15

Thanks for the reply

Sun, 2020-04-19 08:10

Thanks for the reply Sea-Kem,

 

I will definitely get a good cleaning regime going now I know what can happen silently below deck.

 

As I said in the post above, I have had the boat less than a year so unsure of the history and cleaning before then. I would think (or I would hope) I haven't done that damage in less than a year but I will be sure to thoroughly clean now.

 

Tank is repaired and I will clean the hull and reassemble. Should be good for a while longer now.

 

Cheers,

Trav

sea-kem's picture

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 Hopefully a wire buff job on

Sun, 2020-04-19 10:36

 Hopefully a wire buff job on the worst areas and scotch brite pads. 

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Love the West!