Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Aluminum Boat Windows -- Re-anodize, clearcoat, or paint?
RFQ: In the Washington, D.C., Baltimore and eastern shore of Chesapeake Bay area, I am looking for some shop that can anodize or clear coat some boat hatches I have two large (2' x 2') and four small (10' x 10") lifting hatches on my sail boat. They are made of cast aluminum and they surround tinted plastic windows. The cast aluminum was painted white back in 1988, and is now flaking off of both upper and under surfaces. I wish to remove the white paint and then anodize or clear coat the aluminum frames. I sanded the white paint off of one hatch, and liked the bright aluminum look - - and thought perhaps it could be anodized or clear coated - - and thus resist the damage caused by constant exposure to sun and salty water environment. I found, however, that I didn't have the appropriate experience or tools to properly remove all the paint, and to make sure the aluminum frames around the plastic hatch windows were properly and neatly done. Anyone out there who can take on such a job? Or give advice? Thanks.
Roger S [last name deleted for privacy by Editor]finishing cast aluminum - Chestertown, Maryland, USA
2004
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
Do I need to re-anodize aluminum after stripping off paint?
Q. I have removed the black paint and yellow primer from a set of aluminum boat window frames, using a methylene chloride-based paint stripper (sold in Canada as LePage Poly Super Strippa) and 3M stripping pads. If I understand things correctly, the process of removing the paint should not have damaged the anodized finish. Is that correct?
Would you advise having the frames professionally re-anodized? Or should I apply some kind of coating? My goal is a natural aluminum finish that is maintenance-free. The frames look fine now that the paint has been removed; I just want to make sure they stay that way.
Ross Laverconsumer - Ottawa, Ontario, Canada
2005
A. Anodizing aluminum comes from dipping in acid and the surface is oxidized. The oxidized surface is much harder than bare aluminum. Its unusual to paint an anodized surface because dyes can be added to the acid bath to make a colored finish. As long as you don't scratch the surface the anodized coating is ok. I'm sure some chemicals will attack the coating. If the anodizing is removed the aluminum tends to wear off on your hands leaving gray imbedded in skin.
Jim Feig- Mansfeild, New Jersey
2005
Thanks for the advice, Jim. I checked it with a voltmeter - the aluminum isn't conductive, which I guess shows that it is still anodized. There are a few minor scratches, but I can live with them. So on the assumption that the scratches won't cause problems in the future, I think I'll leave the frames as is.
- Ottawa, Ontario, Canada
2005
Caution! Hi Ross. Methylene chloride aircraft stripper is harmless to most if not all metals. If there was anodizing on these frames, you didn't hurt it. But it is environmentally unfriendly, really noxious stuff -- it demands rubber gloves ⇦ this on eBay or Amazon [affil links] , goggles ⇦ this on eBay or Amazon [affil links] , and working outside and upwind for good ventilation.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Re-anodizing cast aluminum hatches and port lights
Q. Hello, I wanted to know if cast aluminum (Almag 35) parts can be re-anodized 10-15 years after they were initially anodize. Will this compromise structural integrity of the part? The parts are cast hatches and port lights used on boats (boat windows of sorts). The frames are made of cast aluminum and at the initial manufacturing time they were clear anodized, can this process be redone on these hatches/port lights?
Tavinder ChannaMarine accessories and repair - Toronto, ON, CANADA
2006
A. Of course they can be re-anodized.. They are aluminum! However you may not be as pleased with the rework as you were with the original finish. It just depends on the oxidation that they have been subjected to, as well as the overall looks of the part in its current state.
You can take the part to a plating shop and they should be able to tell you what to expect more accurately than I could here without seeing the part myself.
You will need to strip the old plating off of the surface in a Nitric based stripper or other acid based stripper and prep the surface as you would in any other situation.
Make sure you do not etch the part as the silicates in the casting will become more exposed and will cause the plating to look undesirable.
Good luck with your task.!
Ryan Cook
Toccoa, Georgia
2006
Q. My name is Gary McPhee. I Live in Berlin, CT. I recently bought a 1988 Cape Dory Trawler and am in the middle of a massive restoration.In preparation for a total paint job, I have been removing anything that touches the painted surfaces of the boat; which brings to my issue at hand. I have removed all 6 windows and brought them home to restore. It is my sense that these are a high quality product that have gone untouched in a marine environment for almost 20 years. There is a lot of corrosion that needs to be dealt with. At this point in time I have not figured out how to remove the sliding windows without ruining the plastic slides that also seem to keep windows. The glass and the associated slides are also in the way of addressing the corrosion in the grooved areas.I do not know what to use to address the corrosion or if I should bother with the grooved areas. Although nobody sees them but me, I can't help but feel that I need to do a total repair so as not to encourage a rapid return of this problem. I have sanded 1 window already, but I think I need a chemical process more than a physical removal. Any guidance you can render is appreciated greatly. Thank You very much- Gary McPhee
Gary W McPheeconsumer - Berlin, Connecticut, USA
2007
A. You can try 5% ammonium citrate solution,pH must be 7-8. Dissolve 50 gm citric acid in 1 lit water and add ammonia ⇦ this on eBay or Amazon [affil links] until pH is 7-8.Your parts are probably anodized and best solution is to find nearest anodizing shop.Hope it helps and good luck!
Goran Budija- Cerovski vrh Croatia
2007
A. Sanding those frames will probably get you in even more trouble. The previous response was correct in stating that they are anodized, they look like raw metal but aluminum frames will almost always be anodized. Read some articles about the process and you will see what I mean. There are many hobbyists that do their own anodizing but the process is a bit nasty. If there is a lot of pitting you may consider anodizing them with a matte finish. The strips that hold in the glass may not be salvageable and you will have to find a glazier supply that carries them. There are lots of anodizing places around and it is not that expensive to get it done except if your parts exceed the vat size. Also check into Cerakote, a ceramic finish used to coat all kinds of metals and has good corrosion inhibition.
Jim AndersonJunkman - Katy, Texas
2007
A. Unfortunately even if you use SS screws, once the screws are tightened, the anodized seal around the screw is broken. With time, corrosion will begin to occur in these areas again. Good luck with your project.
R RoseLookout Boat Window Frames - Beaufort, North Carolina, USA
January 12, 2011
Dealing with corroded Aluminum window frames
Q. Hi -- our window frames are pitted on our boat. Can you suggest a way to clean them?
My husband says we have to sand or acid blast it; I say some sort of wash could do it. Who's right? Or are we both? Thank you!
holly and curt klaverwife of boat owner - Michigan, USA
May 25, 2015
A. Hi Holly. I think you're closer. I wouldn't sandblast it or acid wash it, but would try either Mothers Polish or another specialty cleaner/polish. It may take more than a "wash" though; you might need to use the aluminum polish on a buffing pad in an electric drill for really good results. Best of luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 2015
A. Holly,
I often get sent a part with a "spot that won't wash off" only to determine that the surface has been physically damaged by etching.
A good analogy for this is wood. If you spill something on your wood table, you can wipe it up. If you hit it with a hammer, you now have a dent that can only be fixed by sanding it out. The deeper that dent is, the more you have to sand to get rid of it.
Metal is much the same. When the surface is etched or pitted, the deeper the damage goes, the more work it is to polish down through it. As with sandpaper on wood, you typically start with the coarser stuff and work your way down to the finer stuff. Sandblasting would be at the far end of the "coarser stuff" in this case. If the condition of the surface is bad enough to warrant that and you have the equipment for it, it's probably the faster and easier method. From the photos, I'm guessing it's not that bad, though.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
June 2, 2015
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