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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

anodizing

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worane
1st Mate

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Australia
36 Posts

Initially Posted - 05/15/2014 : 06:05:41

I was considering anodizing my c25 cabin windows. After three days and a couple of hundred dollars in tools and buffing pads I now have them shining ready for anodizing.
I was just wondering how they were finished when new. Were they coated or not and what else could I coat them in. I was think about K2 auto clear coat. I know anodizing would last longer but it is a lot of dollars and travel to get it done.
All thoughts appreciated.
Regards Nick.

Edited by - on

pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 05/15/2014 : 10:38:29

Could you Powder Coat with less prep?

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Lee Panza
Captain

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USA
465 Posts

Response Posted - 05/17/2014 : 07:35:07

Powder-coating seems to be a very effective way to protect the window frames, and it offers the advantage of an incredible range of color options.

When I was looking into it, the glazier that I had approached to cut new glass for me (a PO had replaced the original with shaded plastic) advised me to get them powder-coated instead of anodized. He does commercial work (storefronts and entire office buildings) and has an extensive history with both types of coatings, and he told me the powder-coating offers superior protection as long as care is taken not to chip the surface during installation. He said it's more resistant to minor scratching, which exposes the underlying aluminum to the elements. Neither type of coating can be "touched-up" once it's damaged.

When I had mine done a few years ago I just cleaned them up the best I could by hand (I used a 3M scrub-pad and fresh water, and I spent a bit of time removing the old bedding materials from the glass channel and the inner surface of the exterior flange). The shop that coated them took it from there. So far it has been 100% successful, and they look great.

The most challenging aspect of the operation was deciding what color to use, although my personal choice wound up going conservative with a color similar to dark (brown) anodizing.

Edited by - on

worane
1st Mate

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Australia
36 Posts

Response Posted - 05/17/2014 : 12:32:38

Thank you Lee. your great answer makes me reconsider powder coating.
The reason I am taking a good hard look at powder coat is how many failed powder coated products I have had to make good in the motor home industry when restoring RV's in the workplace.
I have been starting to lean towards just using automobile metallic auto paint complete with a good clear coat over it.Any thoughts on that?

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Dave5041
Former Mainsheet Editor

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USA
3754 Posts

Response Posted - 05/17/2014 : 14:39:16

I have generally been more pleased with quality prep and paint than powder coating. Powder coat is electrostaticly attached and then fused. It is a much cheaper technic in volume production than painting. I would be happy to send you a lot of corroded junk that was powder coated. You pay shipping.

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OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 05/17/2014 : 16:46:32

When I had my window frames re-anodized on a previous 1981 C25, they were dipped in some type of acid solution first. They turned out very nice, not perfect, but they looked nearly new.

I am not sold on powder-coating - yet.

Edited by - OJ on 05/17/2014 17:03:56

Lee Panza
Captain

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USA
465 Posts

Response Posted - 05/17/2014 : 23:19:28

For components that assemble together with close tolerances, powder-coating is out of the question. It is a relatively thick coating, similar to ceramic glazes. Anodizing is a very thin, and relatively hard, oxide layer.

When a ferric item that has been powder-coated has the finish compromised, either by a nick or scratch or too thin or porous a layer that allows moisture to get through, the resulting rust propagates rapidly by lifting the coating and allowing water to wick farther and farther in. Powder-coating on ferric items is notorious for failures. Aluminum seems to be less susceptible, at least around fresh water; I haven't had a chance yet to see what happens to a compromised powder-coat surface on aluminum in a salt environment. I have seen plenty of salt-damaged anodized aluminum, but a lot of anodized marine hardware seems to hold up just fine.

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worane
1st Mate

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Australia
36 Posts

Response Posted - 05/17/2014 : 23:45:00

Thanks Lee,you make a good point there. How do you feel about finishing in auto paint and 1K clear.
No one as yet has answered my question as to whether the windows were anodized in the first place .

Edited by - on

Lee Panza
Captain

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USA
465 Posts

Response Posted - 05/18/2014 : 13:00:51

The window frames had to have been anodized by the manufacturer. Mill-finish aluminum corrodes very rapidly in a salty environment. The original process widely used in aluminum fabrications was a clear-anodizing finish. Later a "bronze" colored finish became popular, especially on window and door extrusions for the building industry. In recent years we've all seen the eye-catching gold, red and blue finishes that look so sexy; it's my understanding that these are dyes that are added during the process. I've been wondering about the term "hard-anodized" that I see from time to time; I don't know whether that's a different process or just a deeper layer.

BTW, precautions are called for in cleaning aluminum components that have been anodized, because the thin oxide layer can be dissolved by seriously acidic solvents and cleaners. The recipes using lemon juice, vinegar and cream of tartar to remove stains also remove some of the anodized layer; the deeper the stain the more of the anodizing has to be removed. This leaves the underlying aluminum vulnerable.

Another precaution to adhere to around anodized aluminum (especially our masts and booms) is on-going abrasion from anything in contact with the surface. Even external halyards that flap against the same strip of surface will eventually wear through the anodizing, and metal components like rings or snap shackles will go through it in a hurry - possibly even faster than it takes for some annoyed neighbor to cut the offending boat's anchor line or mooring pennant ;)

Raw exposed aluminum will usually oxidize to a dark grey on surfaces that drain well, but where water (expecially saline water) that sits in a recess or a joint can develop a build-up of whitish aluminum salts. This kind of oxidation eats away metal and leads to breakage.

If this isn't already information overload, consider also the effect of dissimilar metals producing corrosion of the aluminum through galvanic action. Stainless steel is particularly active in this respect, so a compound like Tef-Gel should always be used on SS screws in aluminum components in the marine environment. Anodizing does not seem to provide sufficient protection against this without using an isolation compound.

As to painting aluminum, it first has to be "pickled" for the primer to adhere. This uses some pretty nasty chemicals, and I'm still not sure if I'd try it at home myself (although some hobbiests have posted on various boards about doing it). There are spray-on products that are supposed to work fairly well, but a good, long-lasting paint job on aluminum requires much more careful preparation prior to painting than do materials like steel or fiberglass. On the other hand, paint can be more easily touched-up, or even removed and reapplied, more easily than either of the other two options.

Regarding the choice of coating on aluminum components, I've wrestled with the same decision - which is why I've acquired this information in the first place. Aluminum really isn't the "maintenance free" "wonder-material" that everyone seemed to think it was back in the '50s and '60s. You can see a lot of shabby aluminum windows on houses from that era. It is certainly a very important material for boats (many entire hulls are made of the stuff), but it has some limitations and it needs some regular attention.

Hope this is helpful.

Edited by - on

worane
1st Mate

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Australia
36 Posts

Response Posted - 05/18/2014 : 22:09:57

Thank you Lee Panza for your concise answer.
What I have decided to do is rough up the now shining polished fascia with 400 grit paper and have metal etched it.
Next will be hi build primer/undercoat,then titanium silver gray base coat followed by at least three coats of K1 clear.
I hope that will keep things together for the couple of years that I have this boat.
My new window kit arrived today from CD. so it should all be together soon.
Mind you I still have to prime and paint the cabin top and sides yet.
Regards, Nick. (worane).

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3754 Posts

Response Posted - 05/19/2014 : 17:19:53

I think Lee's response should be framed and hung on a wall. Thorough and concise.

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Lee Panza
Captain

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USA
465 Posts

Response Posted - 05/19/2014 : 20:09:41

uh...

what does "concise" mean?

I don't think I know that word...

Edited by - on

worane
1st Mate

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Australia
36 Posts

Response Posted - 05/19/2014 : 20:52:57

Lee it means giving much clear information in few words.

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 05/20/2014 : 07:22:08

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Lee Panza
 uh...

what does "concise" mean?

I don't think I know that word...
<hr height="1" noshade id="quote"></blockquote id="quote">

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Dave5041
Former Mainsheet Editor

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USA
3754 Posts

Response Posted - 05/20/2014 : 15:40:51

Most of us don't. We like to hear ourselves talk.

Edited by - on

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