Acid Etch with Zep a Lume

[AK7Buck]

I also have white flowering on my boat - identical with the previous posts. I have used NAPA's aluminum brightener - it works well but only after repeated applications. I just purchased a gallon of Zep a Lume which has a considerably stronger concentration to remove mill scale after one application, based on comments in earlier posts.

My question is should the Zep a Lume be diluted before spraying on the boat, or should I simply spray undiluted? Also, how long should the zep be left on before hosing off with water? I apologize if this question has already been addressed in earlier posts. Many thanks.

[kmorin]

AK7, acid works in part depending on how warm it is (and the metal it cleans) and how concentrated it is.

So if you mix it 50/50 with HOT water, something that ALL manfg's say not to do.... then the effect is like the acid were higher concentration. If you dilute 30:1 you'll be back to the Napa cleaner's probably effects- do it five or six times to get the Zep concentrated results.

If you heat the boat, warm day in the sun, OR a weed burner till the 'dew runs' off the heated area? you'll get more action than if the acid were on a cold boat. So this is a series of related rates where the concentrated acid in the warmest conditions will clean the most in the shortest time and the cooler more dilute solution will be more like the weaker solution you've already used.

Time, spray on (WEAR PPE !!!! full gear and charcoal with dust cartridges on your half face APR [min.] and double gloves and splash goggles and face shield both.... full rain suit and keep hose handy. ) and wait til the foaming actions stops, then rinse with hose. Notice a cold hose wash down will chill the boat so heating again is normal if you want the most from your Zep dollar?

The foaming time will vary with temperature of the acid and metal -warm acid foams up quicker and longer than cold metal and acid; I use the foam as my rinse time indicator.

No fixed ratio, mix some, test a patch low and aft so it won't show and when you're happy with your coverage, speed of cleaning and heat/etch/rinse/heat/etch/rinse cycle- go for it. All that can happen is you'll need to do it again because the days are so cold you get a minimal acidic etch action of the metal's surface.

I've etched in the fall and used straight Zep, and it was expensive compared to a July 15th etch at 2:00 in the afternoon where I used 25% Zep with hot water- and warmed water tank water to rinse. The conditions can be tested however but etching test patches to show you what your conditions need to get your results.

Hope that helps?

Cheers,
Kevin Morin
Kenai.

[AK7Buck]

Kevin,
Many thanks for the feedback!

I have reviewed the MSDS in detail and have put together the following: 1) Goggles; 2) Plastic face mask; 3) Half face aspirator with 3M P100 60923 Organic Vapor/Acid Gas Cartridge; 4) Blue nitrile inner gloves; 5) Neoprene outer gloves to elbows; 6) Rubber boots; 7) Rain suit, with apron.

I will start the process this weekend but unlikely to complete the boat until next spring / summer. I can finish the outside hull and parts of the back cockpit that are showing, but will need to pull floor boards this winter to determine how much more etching will be needed. I may need to pull carpet - yes, what a mess. Some of these boat builders should know better.....

You are a host of outstanding knowledge - I just read your older comments regarding placing a single ground off the battery to the hull. In addition to the flowering, I also have several areas of pitting - and precisely, due to painted back swim step, painted Honda outboard motor, and protected bolts through the transom. Next project is to establish a single ground to the hull.

[kmorin]

AK7,
I know that lots of builders are not aware of the correct design, care and treatment of the metal boats they build!! I've had more than enough soap box posts here to show my frustrations in that area of boat knowledge. However once an owner gets his boat he can begin to correct the short comings and 'doll her up' and then the welded boat will last a long time.

Glad to help, please remember that we all think the only poor question is one not asked.

cheers,
Kevin Morin
Kenai

[Chaps]

I'll throw a bit in here too . . . make sure the metal you intend to etch is clean of grime, grease, dock rash, decal glue, etc., I've found that contamination of many sorts will not necessarily be removed in any acid wash regardless of concentration

[AK7Buck]

Chaps - I was wondering about that while inspecting my fish locker - how much of the grime will the Zep remove. I will clean - I don't want to do this process once let alone twice. Thanks.

[AK7Buck]

The Zep a Lume worked well in most areas of the boat, but not in the fish locker. This area is generally never dry. I acid etched this area several times with very high concentrations of zep. I even pre-heated the locker and still no further removal. I think the best way forward is to start sanding or buffing the corrosion out, starting with somewhat course grade and working to increasingly higher grades. Any other thoughts on how to remove the remaining corrosion?

[MacGyver]

I have a copy of ABYC Corrosion Certification Study Guide and it makes a referencer to http://www.chlor-rid.com/productInfo/index.php for finding and removing salt on boats before painting.

It might be something that would solve problem before you paint.

[kmorin]

AK7,
I'd say the acid had the mill scale and the corrosion pits cleaned out and the rinse water likely took any remaining corrosion components out the drain too? If you're curious and want to test the pits, wet the bottom with a spray or water and let them stay wet overnight. Put a strip of ph strips/litmus paper(drug store item usually- into the pits while they're still wet in the bottom to learn if they're still acidic or more neutral.

If you want to convert the cleaned surface to a more durable oxide like Chromium Oxide then use an allodyne solution after a brief re-etch and rinse- adding allodyne when the surface is still completely covered with rinse water so the air can't get to the surface to form aluminum oxide before the chrome is introduced. Or you can use a self-etching primer paint and top coat with some epoxy or coal tar bilge paint.

I agree with your idea of sanding/grinding cutting down the metal around the pits to remove the entire pitted area would have to be done mechanically. Its kind of important to keep in mind the acid etch (Zep or others) only effects the very top one or two molecules and is then rinsed off diluting the acid to near neutral ph and removing its ability to continue to react with the metal. So deep pits left from previous corrosion would always have to be treated with mechanical means; sanding or grinding or filled by welding.

Cheers,
Kevin Morin
Kenai, AK

[AK7Buck]

Thanks for your responses.

The pitting, although numerous, are not deep. I think I'll start with a DA sander at 500 grit and work my way up, ending at 1500, followed by buffing with scotch brite. I will plan to do the entire locker. Once done, I'll briefly re-zep and then let oxidize and hopefully should be good for the duration.

[kmorin]

AK7,

I'd have to say that 500grit was up in the 'polishing' grits? maybe if the pits are more or less rough spots??? begin in the 100 range? and move up to say 180 an leave it? Not sure why it needs a polish? IF you were discussing a outside panel and were going for some super high gloss yacht finish (?) I might say the grits are apropos? But to clean some pits off the fishhold?

Even Blue or 'fine' ScotchBrite (tm) pads aren't 500 grit! The rough stuff, Brown, is probably 100 or 120 maybe a bit more aggressive? Maroon, middle grit is rougher than 150 and Blue is probably only 150 or maybe 180? not sure on those numbers but I've used sanding buffing and polishing a bit and they seem about right? (welcome to be corrected to those with more info)

Cheers,
Kevin Morin
Kenai, AK

[AK7Buck]

I like your approach better - and agree, no need for a fine polish in this area. Any advantages of using wet vs. dry sandpaper?

[kmorin]

AK7,

Wet sanding is not better that I know about - for the grits we're talking. I'd say get the brown or maroon 3M ScotchBrite (tm) hook and loop pad and see how much it takes to get the swirl pattern to show evening on the surface (indication the tracks are cut deeper than the pits)?

4" won't get into the corners so you may end up with the 2" pads and an air grinder or something smaller to clean the corners using circular sanding?

Cheers,
Kevin Morin
Kenai

[AK7Buck]

Thanks Kevin, I'll give it a shot. Appreciate your help.

In looking at my boat further, I have a couple of very tiny pin holes under the water line towards the bow which I believe is due to poor ground from the motor being isolated from the hull. I will be taking your advice to create a ground to the hull from the (-) post on the starting battery. I run a 26' with a 225 honda and both the boat (back swim step) and motor are painted, and the bolts holding the motor have a fair amount of silicone -- not a good connection between motor and hull. No question this is creating the pin holes. The good part is that I caught all this before any real damage has occurred -- the worst by far is the fish box which was caused by not being acid washed. Many thanks!!

[kmorin]

AK7, how is the boat's restoration and reconditioning coming? Things are cooling down in the neighborhood so boats are lower in all our priorities (except for winter projects) but I'm bumping this up to see how you've been doing and what your explorations are finding?

Aluminum boats are not the subject of the widest knowledge even within engine dealerships and (sadly) some builders' shops too. So if you have a minute to update us on your newest work or even your current point of view- we'd listen.

thanks for your posts, let us know more about your boat? Did we even get a picture of her? This time of year a nice warm sunny scene with an aluminum boat in the middle goes a long way to cheer my winter is coming attitude toward life.

Cheers,
Kevin Morin
Kenai

[AK7Buck]

Kevin,
Thanks for the follow-up!

Yes, I started sanding the fish lockers initially with course scotchbrite, then with sandpaper down to 80 grain, but still have a fair amount of sanding to go. I may need to go lower than 80 in some areas - overall however, it's working. My goal is to get the sanding entirely done on both fish lockers this winter then follow-up with another round of Zep-a-Lume in the Spring when the temperatures are more conducive to etching. While I am pleased with the process, progress has slowed now that I have all winter to work on it. I will also remove the cockpit deck and etch the inside of the hull next Spring. I'll post some additional pictures when done, and a picture of my boat.

I also need to establish a single ground to the hull from the negative battery terminal. On an earlier post, you discussed the importance of establishing a single ground to the hull - closest to the zincs. You had my situation pegged - painted hull, painted outboard, and silicone around the mounting bolts. Should be fairly easy to do. Another upcoming winter project is replacing interior overhead lights with LEDs. Overall, it's important to have boat projects to keep busy during the winter months!!

Appreciate your expertise and willingness to share your knowledge!

[kmorin]

AK7Buck,
If I understood your post (?) you're actually using a buffer down in the fish lockers' bottoms (and maybe sides too?) and the pitting is enough to think about going to a 60 grit to get it sanded out? The test I use is to look at the 'tracks' of the sanding pad on the base metal in the areas of the pits. If a given grit- say 80 will scratch across the pit area then I think that grit will eventually sand it out. If a grit won't draw any tracks over the areas to be sanded down, then I agree it may take a coarse grit 60, (40?) in order to get down into the depth of the pits you're working to remove.

I'll mention some other items to go with this topic. I've long used base solutions to neutralize/counter the acid ph of bilge water. By mixing either baking soda or a few oz. of household ammonia with a couple gallons of warm water (better to mix the solution) and pouring that in the bilge you can help to counter any acidic standing water or any water that has found a home under the bilge stringers where a film could begin the corrosion cycle.

I usually recommend this before the last trailer ride home in the fall so the mix gets sloshed around well but it will work anytime it just won't rinse as widely if the boat is parked. The idea is; if you're concerned that there may be corrosion inside the hull then adding some base to the possible acid solution you're working to get the bilge to a neutral ph of 7. Super strong bases could do some damage on their own.... but the baking soda or ammonia solutions are not in that category.

Just a note about outboard bolts for reference too. Lots of, if not all of the outboard bolts we see are SS and usually not 316L grade which would be better than the 304 grade most often supplied or used. But... if you go to the galvanic scale and look up SS and aluminum they're spread pretty well. https://en.wikipedia.org/wiki/Galvanic_series you'll see the spread from Nickel/SS (304) "Active" - to aluminum; is greater than from aluminum to zinc?

So unless you passivate the 304 (SS in general) zinc plated bolts are less likely to corrode in the aluminum bolt holes. Passivating SS is easy, there's an acid gel that you can bathe the parts in and it creates a 'less active' chemical surface on the SS parts that will not be as much a battery as the "active" SS will in the same situation. ( http://www.delstar.com/passivating.html link to better explanation)

Galvanized bolts won't look as nice because of the dull grey finish but they will react less with the aluminum.

Regarding pin holes: I use the Rule of Thumb that if the hole is in the center of a quarter-sized crater that may well be stray current corrosion but if there is any bilge water, electrical wiring, fittings (like copper or brass) or ANY other materials near then the culprit search should be expanded to include the other materials or locally occurring corrosion cell. Stray current corrosion in my experience comes in a more wide spread set of pitting spots, and usually shows up outside the the hull. So if the pin holes are inside out, that seem to me to argue the cause came from inside. If the pin holes are part of outside-in pitting and then I'd want to look for other pits and last, depending on the trailer bunks- pitting or bunk rot has happened to many aluminum boats too.

Thanks again for your continued posts, you don't need to wait to post pictures of the boat- as far as we're concerned!

Cheers,
Kevin Morin
Kenai

[AK7Buck]

Yes, exactly. I have gone to 80 grit and finally see ‘tracks’ of the sanding pad on the metal, and it is working. Ideally, not as fast as I would like so I thought about moving down to a lower grit for certain areas. The bad areas are on the bottom of the lockers; the sides are not bad at all. I very rarely have any water in the bilge – at least from what I can see. I like your idea of stabilizing the inside of the hull with baking soda – I will do that next year.

I have signs of “flowering” towards the outside of the bow below the water line, and inside the hull along the bunker boards. As a result, earlier this year I replaced the carpet bunk covers with plastic from Gatorbak out of Minnesota (gatorbak.com). Overall, very pleased – they are holding up well. And they are not overly slick – no concerns backing down the ramp, and the hull of the boat dries out very quickly.

I do not have any pin holes on the aluminum, but there is bondo material that the manufacturer used to fill-in areas that were welded from the inside (yeah… no comment). These pin holes are on the bondo on outside of the boat; I filled them in with 5200.

My guess is that I don’t have a good ground on the boat – the motor is likely isolated from the hull due to paint and silicone. Ironically, the bondo with the pin holes is towards the bow under the water line. It is not anywhere near the bunks or the zincs. The zincs are in excellent condition, both on the boat and the motor. I do not have a single ground to the hull - in fact, I have nothing grounded to the hull at this point, at least to my knowledge. That’s why I think your idea of establishing a ground from the negative battery terminal to the hull near the zincs may address the pin holes. I also had problems with stainless steel coming in direct contact with the aluminum in several spots – these areas have now been isolated.

Thanks Kevin.

[kmorin]

AK7Buck, not sure I fully understand the builder/manufacturer using bondo to fill outside for a weld inside? Seems odd but worse it seems to imply the weld sucked back or left a recess outside the hull where I'd have expected a bulge or proud spot?

Anyway, I've missed this detail in the past posts, not sure that the pin holes were in filler so not coming through the hull. 5200 should do the job?

Very common not to have an electrical system bonded to the metal hull, lots of builders still say that is in correct and if they were listed the names would be household/very familiar/well known brands. So installing your own is a good step. IF the bond from the batt. Neg is to a large longitudinal or from teh engine's starter Neg.Post and out to the transom's main structural elements(?) then the bond doesn't have to be physically near the zincs to work is preventative purpose. The hull will conduct any stray current to the zincs if there's a bond to the hull that keeps there from building a voltage potential to the hull 'proper'.

But the holes in the plastic filler are not related to any hull corrosion issues, those holes are usually a reaction when the filler is applied where the gas could not escape before setting up OR mixing was done too fast and some air was entrained in the plastic filler, at least I can't see any electrical interaction with non-conductive materials?

Cheers,
Kevin Morin
Kenai