Painting aluminum

[REBrueckner]

I'm trying to figure out if it's feasible to properly paint the aluminum rubrails on my YF.

I'd appreciate any recommendations. It looks too me too much for an amateur. (I could not find any specifics in previous tech discussions.)

Awlgrip has five different systems for aluminum:

(1)Aluminum to be heavily faired, where Alumiprep 33 Acid Cleaner and Alodine 1201 Chrome Conversion Coating will not be used.
(2)Aluminum to be heavily faired, where Alumiprep 33 and Alodine 1201 will be used.
(3)Aluminum which requires little or no fairing. Alumiprep 33 and Alodine 1201 will be used.
(4)Repair of blisters caused by corrosion on previously painted aluminum.
(5) Anodized parts where Alumiprep 33 and Alodine 1201 cannot be used. No fairing required.

The Awlgrip text says in part:
"...Alumiprep 33 and Alodine 1201 can create an excellent anti-corrosive base for a paint system. However, both products are very aggressive acids which require very careful handling and a thorough assessment of the project before they are used. There are many situations where the use of these products is not practical..."

It sounds like approach #5 applies to anodized, rubrails, but the text says
"... This is designed for the coating of smooth parts which required no fairing or filling. In almost all cases, using Alumiprep 33 and Alodine 1201 would provide a better system; this system is provided for situations where physical or regulatory restraints prevent their use.

So my first question is, can the acids be used safely on rubrails? I don't think so because the text says insides must also be rinsed of all acid. And I would be afraid rinising down on the topsides would be a disaster. Anybody used these acids on rubrails?

Ok, if we shouldn't use the acids, then does the wimpy #5 approach work? I don't mind if I could get eight or ten years, but for two or three I'll let the existing look remain. Also, here the text says a zinc chromate primer must be applied one mil thick (wet)...I've never sprayed paint, so I don't know if this is a no brainer or really takes skill. Can it be done with a brush? The text says too thick a primer will "...split or peel..." No an encouraging comment.

Thanks for feedback.

 

[67hat34c]

I have done aluminum painting. the problem you have is the corrosion is very hard to completely get rid of. sand blasting is the only way to get rid of most of it. you will have to remove everything from the boat and sand blast the parts very heavily, acid wash with alumiprep and coat with alodine then paint with epoxy zinc chromate. then if there are areas to fill, do the filling, sand then touch up bare aluminum with the zinc chromate. then 545 primer and awlgrip top coat. The paint shop that i buy awlgrip from did not like awlgrip zinc primer, instead they like the dupont, I have the code number at home. anyhow my window frames were badly corroded and i did this process and it has been over 2 yrs and nothing came back, now this is not tosay it will never happen but thus far we are good. recommen that you find a way to completely insulate the ss bolts and screws from the aluminum, use nylon or teflon bushings and washers this is the only way to prevent the stuff from comming back. now back to sand blasting, you must realy hit it hard especialy areas that have corrosion. need to open up inclusions. these can be a pin head size place that is actualy a large cavity that you cant see.

it is alot of work and if you are handy with a paint gun and are brave enough for sand blast then try it. secret is that you must coat bare aluminum very quickly , as in within a few hours oxidization starts immediately. in this case sandblasting all parts first then acid wash and alodine parts that you can get the green primer on within a few hours of cleaning. wear laytex or vinyl gloves, never touch the bare aluminum.

 

[thoward]

Not sure but OSPHO might work?

 

[StratPlan61]

You must have a good reason for wanting to paint your rubrails, but I wonder if a highly polished aluminum rubrail might not look GREAT with any hull color? Seems like the easier and cheaper way to go - I know I am suggesting the obvious, but polishing would almost be 'no maintenance' compared to anything else? Just my .02 worth.

Bear'
1984 61' MY Strategic Plan

 

[DeeRow]

Once you go to all the trouble of painting the rub rail, what is going to happen when you use the rub rail? Window frames generally don't get rubbed. The local yard talked me out of painting the rub rail. They said it will look great launch day, but will not hold up. They suggested replacing the rub rail as the cost will be almost the same as paint and will look better longer. Not sure if you can find the same rub rail to replace your current rub rail.

Mark

 

[Maynard Rupp]

I am surprised that you have an aluminum rub rail, ours is stainless. If you do paint your aluminum rail, you must remove it so you don't trap stuff on the probably hollow back side. When you are done, do as the Bertram owners do and install a stainless rub rail over your aluminum one. Make sure the rail material is solid, not a piece of curved sheet metal. Those cheaper hollow ones flatten out when you bang the dock pilings. here is no way I would use aluminum for a rub rail, it will look awful in a short time.

 

[captddis]

In short DO NOT paint old aluminum. I have never seen it work for long. I would second the suggestion for just polishing. I have dealt with many Bertrams and their aluminum and even doing everything by the book it does not last. Dave

 

[exsailor]

All these experienced coments about aluminum ..... again I will ask has anyone heard of any 53's having an aluminum bow pulpit????
exsailor

 

[Paul45c]

I saw a really tired old 58YF that had a diamondplate bow pulpit -- never seen that before. It wasn't executed well, believe me.

 

[captddis]

A lot of the old 53s had the Ideal aluminum pulpits.

 

[luckydave215]

OK, I guess I'll weigh in.
I produce sea going aluminum parts for a living, and have 30 years experience with coating them (what works and what doesn't).
Forget trying to paint corroded aluminum parts, it's a waste of time. They will look good for a while, then the oxide will come right back, this time under that expensive paint. Aluminum exposed to a salt water environment (including on deck, window frames, etc.) suffers chloride ion penetration, all the way through the part, even if it's 5" thick. This occurs almost instantly. A part that has been in the (salt) water overnight can't be anodized sucsessfully.

The sea is harsh on aluminum.

A proper coating job on new aluminum parts is as follows:

1 Design the part so no dissimilar matals are in contact. Stainless steel screws in aluminum parts are a disaster.

2 Hard anodize the parts with a zinc dichromate seal.

3 Prime with zinc dichromate epoxy primer.

4 Undercoat with epoxy "undercoat".

5 Top coat with epoxy (color coat). Bake on.

6 Top coat over the top coat with linear polyurethane. Bake on.

7 Protect the part with zinc anodes.

If you scratch through any of the coating after you're done, throw the part away.

 

[jim rosenthal]

When Blue Note was painted, I had this dilemma with the window frames. The shop that painted the boat (Aircraft Refinishers) was experienced painting aluminum. They buffed it down to the bare metal, did the full Awlgrip prep with Alumigrip and Alodine etc, and then primed it. The final coats were Imron in aluminum color, and Imron clear over that. It has held up fine. (sorry Dave- maybe I have just been lucky for once)

I would not do this on a rubrail, though. The life of a rubrail is guaranteed to remove anything that's been put on it. Would it be practical to change over to SS rubrails? they hold up a great deal better, I find.

 

[captddis]

Jim,
Glad it worked for you. I remember a Bert that a guy took some hardware store paint and brushed it on the Alum. sheer guard. 5 years later still fine. Sometimes the gods shine on us. FWIW on the window frames I have found that sprayed on rustoleum holds up better on window frames than Awlgrip. I think that the enamel breaths a little and you do not get the blistering. A number of years ago one of my friends/ cust wanted his wood Guthrie SF awlgripped. The yard said not to because the Awlgrip would cause the wood to dry out. We laughed and had it done, a year later all the windows started to leak and the frames shrunk and opened up.
I know a number of people who have had their aluminum half towers and davits stripped and powder coated with good results.
I believe that rubrail in question is actually the extrusion between the deck and rubrail. Hatt did these for a few years. Dave

 

[luckydave215]

I suppose we have different definitions of "last a long time". I'm thinking 20+ years.
Towers and rub rails are usually extruded out of 5000 series alloy, and it holds up to salt better than the more common and much stronger 6000 series (6061) that structural parts are fabricated from.
Expensive marine aluminum parts are built using 5086, it's the best in salt water, but hard to get in anything but sheet.

 

[dwaynec]

When we bought our '72 48YF the PO had painted all the aluminum parts on the boat, including the rubrails. They didn't look too bad when we bought the boat, but within a couple of years things took a decided downhill turn. Most of this may be because of poor/no prep prior to painting.

Long story short, when we painted the hull last year, I sanded all the paint and anodizing off the rubrails. The anodizing was in pretty poor shape too. I sanded to 320 grit with a DA sander. This spring I polished the rails with Flitz. They came out looking great. I did not wax the rails after using the Flitz as it has what seems to be a type of wax in it. The old post with pictures should still be here somewhere. I think it was last May when I made the posting.

They still look pretty darn good, but I know that in the spring I will get the opportunity to once again polish the things. Oh well, hopefully it will be less of a chore this year than it was last.

 

[34Hatt]

They buffed it down to the bare metal, did the full Awlgrip prep with Alumigrip and Alodine etc, and then primed it. The final coats were Imron in aluminum color, and Imron clear over that. It has held up fine. (sorry Dave- maybe I have just been lucky for once)

I think you have been lucky Jim when I did mine I did all those steps had them looking like new. Did all the recomended steps and the are starting to bubble under the paint which was Stering. I have to agree with Dave and feel Alumium just does not belong with salt water in most cases
Also my frames where only 6 years old P.O replaced them and they were powder coated and were peeling when I bought her.

 

[Paul45c]

LuckyDave, what are your thoughts on reanodizing frames back to the original bronze color and NOT painting -- still no go with used frames? David Pascoe was recommending to get pits rewelded and reanodized in one of his articles I read. I actually like the old bronze anodized color, and at least you don't get the blistering paint.

 

[luckydave215]

Welding up the pits and re anodizing is the only way to go short of replacing the frames. Make sure the welder grinds out past the affected stock, and a bit into clean base metal. The corrosion goes deeper than you can see. The welds will show a little, because the filler alloy is a different composition than the base metal. You can see the welds in the corners of the original frames, new welds will look similar.
The bronze/army green (depends on how the light hits it) color of the original frames is hard anodizing with a nickle acetate seal. If a part is to be left unpainted, nickle acetate seal is used, if paint is going to be applied, a zinc dichromate seal is used.
The window frames on my boat are still in perfect shape, with no corrosion I can see, and I know how to look for it, but they may have been replaced (a few times.............)

 

[REBrueckner]

Great feedback, thanks, I won't be painting..
How about polishing: dwaynec said: "... I sanded all the paint and anodizing off the rubrails. The anodizing was in pretty poor shape too. I sanded to 320 grit with a DA sander. This spring I polished the rails with Flitz..."

This sounds more like my speed....I'm an old wood boat sander from waaaaay back.

Is this the preferred method? If so what's a good grit to start with and how do you know when you are done..uniform color??...I'm sure some small pitting would remain...Is this a problem?? Others have also recommended Flitz.

 

[luckydave215]

Bare, shiny, polished aluminum in the marine environment will stay that way for about a minute and a half................