Corrosion under flooring on Alumaweld Intruder?

#1

I bought a used 2002 22' Alumaweld Intruder last year which appeared to be in ok shape. When I removed the flooring it appears I have some corrosion issues and it is very dirty. I am trying to figure out how to stop the corrosion that has started. From what I have read maybe I should use Alumunum Brightner to Acid wash the surface then polish it with something like mothers and fill in the little corrosion spots with something like marine jb weld? Or should I coat as much of the surface I can reach with something like coat-it or gluvit? If anyone has options that have worked for them I would appreciate hearing them. There are some areas of the boat that I cannot see like inside the box beams and underneath the fuel tank. The boat is stored outside so rain water can obviously get under the flooring and flow out the drain plug. I have attached a couple photos of the areas.

Thanks

http://i683.photobucket.com/albums/vv19 ... D_EB4A.jpg

http://i683.photobucket.com/albums/vv19 ... D_ABD0.jpg

#2

giddy, first its always good to cover the course already charted here, it sounds like you've done some research but take time to read what we've all posted thoroughly. Then most of your questions will be answered.

Corrosion of aluminum is of two main types galvanic and crevice/poultice; in the first there are different metals so a 'battery' if formed-aluminum looses. The second is more complicated but relies on an acid cell or some place where the concentration of liquid can become acidic and a cycle of corrosion occurs where the water looses oxygen and becomes acidic then is diluted with more water, and the cycle repeats.

To stop the first get rid of metals (on or in water) next to the aluminum. To stop the second neutralize the acid formed by de-aerated water or poultice cells. Fill a 5 gallon bucket with warm water dissolve a couple of table spoons of house hold ammonia, or a box of baking soda- then flood the bilges and let it stand, then rinse for a day with a garden hose at the bow forefoot under the deck in the bilge with the trailer bow up to drain the rinse.

This will stop the corrosion not cure it. Next find the cause, in the pictures it appears there's a coating ? or some film on the metal. Unless put on correctly that is the cause of your problems. The water has permeated the water proof but NOT vapor proof coating that was not put down on a properly chrome or zinc oxide film (just put on to aluminum oxide) so as soon as the paint blisters, the cells begin and you have what you show.

It would be best to sand blast the entire bilge - not easy of course. Next is a paint stripper (the real poisonous toxic killer stuff not some 'green' useless goop) and get the paint off/out. Then use etch, and leave the bilge bare. OR if you're painting etch, Allodyne when wet during the rinse, and then prime and then topcoat. Coal Tar epoxy is vapor proof, but bare bilge won't hurt the boat if the ph is tended.

ph strips will tell you the amount of acid % in you bilge water so you can neutralize. or dilute to the extreme where the ph is within a point or two of neutral (7)

hope this helps some?

Cheers,
Kevin Morin

#3

Yes thanks Kevin. After looking at it closer it does appear that there is some overspray of the zolatone paint they used this could be the cause of corrosion you describe. Could I instead of sand blast the hull could I sand it with 120 grit or just try and see how well the acid etch such as aluma brite cleans it then leave it bare or sand it after the acid and leave it bare? I don't really have a desire to paint it and everything I have read leaving it bare is the best like you said. I wish they were a little more careful on their spraying.

Is the baking soda treatment necessary even when acid washing? This is where I get confused. Sorry for all the questions, and thanks!

#4

giddy, there's only two ways to clean; blast or paint stripper followed by acid etch, sanding will only work (acceptably) on outside flat surfaces. Sanding will leave coatings in the inner corners where the tool can't clean well. Sprayed chemicals will reach these locations.

Not sure you're reading carefully, giddy? Soda neutralizes (its a base); when should you neutralize? After using acid or when acid forms incidentally. Can you avoid neutralizing? Yes by extreme dilution to attain an effectively neutral ph from the huge volume of neutral ph tap water slowing diluting the acid to become nearly neutral.

There are terabytes of data about Miracle Metal corrosion on the web, there are plural megabytes here too, please take time to read the site and see the many articles where this has been discussed over and over and over and .... (typing fatigue))))).

Cheers,
Kevin Morin

#5

Another question if you have the time. I was looking at your posts about acid etching your boats and I have been debating on doing that to the outside of mine also. On the sides, I am planning to acid wash it and then mechanically buff it for a nice finish and leave it dull over time but the bottom I would just leave it the white color that the zep alume or aluminum brightener makes it. I just pulled off some factory vinyl stickers and it is very shiny underneath so I doubt it was ever etched? Here is a picture of the side where the vinyl was and a picture of the bottom that I would etch and leave. There are a few barnacle remnants on the bottom and maybe the white flowers you describe in other posts. Would you recommend my methods for longevity of the boat? This boat is no longer moored and is trailered to the ocean.

Thanks Kevin for helping me understand. Now I will start working.

http://i683.photobucket.com/albums/vv19 ... D_0071.jpg

http://i683.photobucket.com/albums/vv19 ... D_B0C5.jpg

#6

I have a small 2008 Alumaweld, not the sterndrive like yours. I haven't noticed any corrosion, but I guess I better check.

#7

giddy, do the buffing first then etch, follow with a rinse and leave the metal to oxidize. Buff patterns will show, I'd suggest using a belt sander with ScotchBrite (tm) type abrasive belts if possible? [this tool requires a fairly high level of planning and effort] OR you can use a 7", 5" or 4" Scotchbrite (tm) hook-n-loop round pads on a circular sander/grinder and buff the mill scale and scratches off that way. Begin with the brown and move through maroon to blue- lots of work.

After you're all done mechanically working the surfaces inside and out; then etch.

Cheers,
Kevin Morin

#8

Thanks again Kevin, I was just worried about leaving the white etch surface but everything I have read says it will oxidize fast it will just stay white and not the dull grey? Also is there a place online anyone would recommend ordering 7" scotch brite hook and loop or maybe the belt sanding belts? I was thinking about this site http://www.abrasivesaver.com or amazon. I will see if I can find a belt sander, I might just pick up a 3"x18" one from SEARS.

Also if I am sanding the entire bottom is there an easy way to jack half the 22' boat off the bunk (at a time to sand and etch) or is there and correct way that I should be doing the whole thing?

#9

giddy,
aluminum oxide is initially formed to about 2 mils in a few seconds, the other couple of mils of depth of older oxide takes days or weeks. But oxide formation stops about 3-4 mils deep and that's one of the properties that makes this the Miracle Metal; it heals it self- if allowed.

The surface color will darken over time. The white metal look of a fresh etch will fade and darken but it doesn't hurt anything to do it again periodically if you're concerned about that color?

http://customsandingbelts.com/ they don't list their Scotchbrite (tm) custom belts online if I recall, but if you call/write/email the products are there. I use these folks for more almost all abrasives. It's A&H Abrasives and they're part of Woodworkers Supply.

Cheers,
Kevin Morin

#10

Thanks for the website they got back to me quickly and are definitely a lot cheaper than the scotch brite belts.
Is there anything bad about using standard 120 grit on the inside before I acid wash since it doesn't have to be perfectly smooth since it is covered by flooring?

#11

giddy, 120 is kind of light to begin your work, think 80 grit to take off the paint remnants and junk in the blige and scratches outside.
Even 60 is Ok for a first pass, then go to other grits and end up @120

Cheers,
Kevin Morin

#12

Thanks Kevin, I started sanding yesterday lots of fun. Also lots of fairly deep pits which are hard to clean on the inside all the way up to behind the front fish hold, so I am using the paint stripper with sanding on those areas. The deep pits have me a little worried and I am contemplating painting with the Coal Tar epoxy that you listed earlier. If I put down the coal tar epoxy does it fill in the pits and do I need to put a top coat on it?

One last thing for this morning, if I decided to sand blast what medium should I use? The reason for sand blasting of course is I am not happy with my sanding and I could reach under the gas tank better by sandblasting. My grandpa has a sandblaster at the dairy 15 minutes away and I am sure I could use it one of these weekends.

Or should I just buy a soda blaster like this one http://www.harborfreight.com/40-lb-port ... 67625.html

#13

giddy, pits in the hull are just that; "the pits".

First you have to clean them out to evaluate them, then if they're "too deep" you have to repair them but if you leave them then they need left so they don't get deeper and hole the hull.

Blasting with soft white sand (water filter sand/soft silica) works OK, some people use glass beads and others use soda type particles. As long as you have a careful touch any media will work for blasting media but the softer products will give you more time on a spot without excavating the parent metal in 'good' places. Deciding whether to area or spot blast usually influences what media- area blasting with cheap sand is affordable while spot blasting with some higher priced media will clean pits if you're in close using a very small nozzle?

Once the pits are cleaned, you'll need to gauge the depth? I'd lay a short straight edge over the pit to flat area and see with a hand light what gap is under the edge in that pit. Then I'd TIG weld the one's that were 50% deep IF possible? Sometimes welding is hard to access inside the bilge but unless you do weld repairs there is no sense doing any other non-welded work on the pits.

Somewhere here at AAB I've posted an image of a corrosion site in 3D. Please look it up and then use a carbide round tipped bit to gouge clean to bright metal the worst, deepest pits and insure there is a shiny bottom crater not one with a black or white line at the bottom; this color indicator can mean there is more to the corrosion pit than meets the eye. My caution in this matter doesn't include the small 1/8" round spot that is only 1/16" deep and has a very shallow pit.

To find out if any paint is truly vapor proof, contact the vendor. The best, for your purposes, is to contact Amercoat PPG. They don't make cheap stuff but figure if some of their products are used inside steel tanks to hold drinking water..... well they'll know vapor proof and will have 'bilge paint' products. Now it's to be expected that one gallon would make a mortgage payment so don't expect home handyman pricing.

Once cleaned of the material inside the corrosive cell by wire wheel, sanding, blasting and then etching; the metal will form aluminum oxide again so there will be no further corrosion if you've found the source?

We're assuming a paint film created a crevice/poultice site and that is being eliminated. But if the cells were from a copper fuel line in the bilge water? it's still a matter of finding and eliminating the source. Coal tar or any other paint will not improve the corrosion sites' remaining hull metal endurance if the coating is not applied with all the steps mentioned; mechanical cleaning, acid etch, Allodyne while wet, drying, primer then top coats. Bare metal will last just as long if you keep the bilge water neutral and rinse the boat regularly, won't look as good but it will serve as well.

Cheers,
Kevin Morin

#14

Well after sanding awhile and looking at how much space I can't reach under the fuel tank, plus the fact there is foam on the sides of the fuel tank which I have read is a bad thing, I have decided I will drain the fuel tank, cut the cross members above the fuel tank and take it out. I will then walnut of glass bead blast the rest of the inside. I may even blast the bottom it you think it would be a good idea before etching. Looks like I can get 50lbs of 80 grit glass beads for $42 from Harbor Freight or 25lbs of fine or course walnut shells for $24. I found 100lb bags of 90 grit silica (white sand) at a local store for $13 so I will probably go with this and be gentle.. Do you think that should would work? Also any ideas of how many 100lb bags to do the inside lower hull of a 22' alumaweld? Here is a picture showing the fuel tank and cross members with half the boat sanded.

http://i683.photobucket.com/albums/vv11 ... 16EF3C.jpg

Talked to a local welding company today, they claimed they would tig weld whatever large pits and mig the cross members back in.

#15

Well I dropped it off at the welder this morning, got finished blasting with the tank removed. There are a lot of pits they said they will look it over and get the big ones. Probably around 4-5 hours of labor. Then I will get it back acid etch it put the fuel tank in and have them weld the cross members back in!Hope this will be the last time I have to do all this. I also ordered some Tef-gel for all my SS decking screws that have corroded the holes, which I have also sand blasted and will etch with the rest.

Thanks a lot for your help Kevin. I will post some pictures when it gets back from the welder along with the rest of the process.

#16

giddy, the best way to install SS hardware/bolts/screws is to use an isolation bushing where the aluminum is over-drilled to the OD of the plastic/nylon isolation tube (bushing). Then the SS is lined by plastic instead of TefGel which helps but is not the best practice.

Nylon washers and bushings are available http://www.keyelco.com/products/specs/spec43.asp or
http://www.alliance-express.com/fasteners so the best fix is to re-install like 'it should have been done' in the first place.

I still use TefGel to bed the plastic and there is another very nice product that helps to seal -not inexpensive but a nice product: http://www.apmhexseal.com/self-sealing_ ... bolts.aspx

I know I'm encouraging you to do work in a yacht-like finish but why do it over again and again? Do it right once and the install should last. I also realize I'm sitting at the key board spending your money like water; and "that can mean the difference between the couch and the garage" -as Red Green used to say.

Cheers,
Kevin Morin

#17

Thanks Kevin, I had thought about lining the holes for my kicker with nylon bushing but never thought of the deck screws. I will go to the local fastener shop and see what they have, I assume the nylon bushing are just pressed in or do you glue them in with something like 5200?

I really hope the welder does a decent job and gets all the large pits, and hopefully the boat will last me for awhile now!

#18

giddy, this is where mail order is the best so you can get a 'kit' of the needed sizes, unless your local store has some reason to have a super wide selection of bushings and washers on hand? I keep a kit of the correct bits and bushings with TefGel and Locktite white thread paste to install. The first is to drill the 'right size' to get the pattern and then dry fit, the fasteners and the hardware. Then over drill to the bushing size and put them in, add goop to the surfaces and plastic washers/bushings and white goop to the SS threads and make 'em up.

Cheers,
Kevin Morin

#19

Thanks I think I will order some stuff from http://www.alliance-express.com/insulator-washers after I measure and count what I need. I wish I didn't have to but I think I am going to have to put some foam back in so the gas tank can't move side to side. I was thinking about having a couple of ears welded on to bolt to but I just don't like the idea of welding on a used tank.

#20

giddy I know what you mean about tank welds, I've had one go up so I'm not advocating it unless the welders are willing. But... foaming the tank in is just asking for future deterioration.

You can make a tank saddle/bed/brace/cradle in the bilge like a couple of frames with the shape of the tank recessed into the center and lined with flat bar. Then use UHMW tape as a bedding/isolator strip and lay the tank in the two (or three) beds and a top strap/deck beam to retain it. Avoid any brass fittings in the fuel lines, and tank fittings so you don't create a "galvanic bilge mixture" and leave the tank to 'breath'. It will last longer, most of them corrode inside out from water left in the tank in droplets that become acidic.

Cheers,
Kevin Morin

#21

Thanks I will take a look at possibly creating a cradle, hopefully it is feasible. Currently it sat on 6 or 8 plastic 6"x1/4" spacers on the bottom of the hull with 4 pieces of angle in the corners with a little gap between the runners which were filled with foam, maybe I could mount some plastic the 9' length along the runners that would take up that gap and hold the tank from shifting side to side. I will definitely give it a look before putting foam back in.

It also had a grounding wire from the tank to the hull where there is also corrosion from the dissimilar metals (I presume a SS screw to aluminum) for this could I just switch to an aluminum screw to avoid the corrosion or do you think there was a reason why they went with SS?

I saw that picture of you next to that exploded tank. Man that looked scary!

#22

giddy, I didn't realize your use of the terms about the 'foamed in' tank. I was expecting the usual poured in foam totally encompassing the tanks' sides but it sounds like your tank will work just replace the foam with something firm and plastic and that will drain downward. The corner brackets welded to the hull and the plastic mount pads all sound OK, not best practice but workable.

I suggested the support frames as I thought the tank was bedded in foam -not the best but a way for some builders to get the skiff out the door.

Tank ground/bond/anti-static lead can be done in copper wire, and a SS stud using heat shrink sealing on the ends of the conductor so water doesn't get into the insulation. There are types of shrink with glue in the sleeve that work best. The ring end joint will be tinned copper (mostly) and that can be put on a SS or aluminum stud as long as both are sanded to free up coverings, and make a good bond; then sprayed with battery terminal varnish/coating/paint to seal the moisture out of the bond areas.

aluminum to copper lugs goes away faster than copper to SS so they used SS to get a longer service from the bond lug.

Cheers,
Kevin Morin

#23

Thanks I will spray some of that terminal spray on the ground lead end.

They started welding the pits today but were having a tuff time getting them cleaner so I said I would pick up the boat and acid wash it and try and clean them up a little more with a SS brush and bring it back to them Tuesday, the welds they did do didn't burn through the hull so I guess that's a good thing. I am planning on grinding the welds back down flush with the surface which I assume is normal practice.

Thanks again!

#24

giddy I doubt the welds will work if not done with TIG and to facilitate that I'd use a carbide burr for non-ferrous metals (long flutes without cross hatching used for steel and ss) an or a drill bit and 'bottom' the craters. This will leave a shiny liner of fresh uncorroded metal to weld.

the welds almost can't be done by MIG since the arc is established by wire/filler advancing; therefore to heat and clean is to deposit filler. This is totally counterproductive in most pit repairs. If your welders didn't have the experience to know this fact (?) I'm very unconfident in their ability to perform the welds at suitable standards of work.

If you can't use a carbide burr and a die or air die grinder? then use a drill motor to 'kiss' the pits and cut them clean to bright metal absent this, a rotary wheel may help but is not really the best choice. Blasting is still a valid choice but is very labor intensive as is putting the burr to clean the pits' bottom surface of chalk and paste.

If the welds are MIG, sanding them will reveal gas bubbles if they're there (?) and if done with TIG is not usually needed.

Cheers,
Kevin Morin

#25

I did sand blast most of the pits and bilge but some I just couldn't see well enough to get into them when the sand was flying. Most of the bottoms are clean but some had a sharp edge that I just missed when blasting. I will try to get into them with a carbide bur, they are tig welding them but leaving a large bump so hopefully the welds are good. I just figured acid washing the pits would clean out the little bit of corrosion left on the outside of the pits and grinding the welds down to the hull when done just makes it look better and doesn't catch stuff?

Here is a photo of the current welds.

http://i683.photobucket.com/albums/vv19 ... 740547.jpg

AluminumAlloyBoats.com

Corrosion under flooring on Alumaweld Intruder?

Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Sanding Equip Source

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under fasteners

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?

Re: Corrosion under flooring on Alumaweld Intruder?