Cleaning aluminum mast
- Thread starter jmce1587
- Start date
The mast is probably anodized. Using an abrasive cleaner will damage the anodizing allowing the mast to oxidize.
I'd be inclined to try some mild detergent cleaners and maybe something like denatured alcohol to clean stubborn stains.
I'd be inclined to try some mild detergent cleaners and maybe something like denatured alcohol to clean stubborn stains.
Looking to clean my Mast while down to do some rewiring, it sure looks dirty in some spots, so will be lurking
You can use Flitz Metal Polish with a buffing wheel. You may want to rethink doing it. While it will look pretty, Dlochner is right. You are removing the anodizing, which is protecting the mast
Years ago a friend of mine spent about a week polishing his unanodized mast. Ended up looking like it was chrome plated. Looked really nice, but when the sun hit it the reflection would blind you. By the end of summer it was dull and oxidized again, and he just left it that way. Anodized aluminum should not be polished.
Last edited:
Aluminum is a great metal. When left in the weather it will form it’s own protective coating. So if you scratch it to clean it in a short time it will look dull grey. If you wash it it will look dull grey. If you polish it it will look dull grey.
On the other hand you can paint it. But then you open up a whole new can of worms.
On the other hand you can paint it. But then you open up a whole new can of worms.
If the mast is NOT anodized and is unfinished aluminum; AND, if you have a bunch of black streaks and other staining... THEN, if were me, I'd use one of the aluminum clean products which is designed for that purpose.
That should, if used properly, involve less work, produced a more even cleaned finish, and return the the mast to as-close-as new condition as possible.
If you do that, then I'd just leave the aluminum as JSSailem suggests. If you want to wax it, it is lot of work that will eventually lead to either doing that again, or may get splotchy.
That should, if used properly, involve less work, produced a more even cleaned finish, and return the the mast to as-close-as new condition as possible.
If you do that, then I'd just leave the aluminum as JSSailem suggests. If you want to wax it, it is lot of work that will eventually lead to either doing that again, or may get splotchy.
When you are cleaning a bare aluminum mast (not anodized or painted), the best thing to use is metal cleaners specifically designed for aluminum that are acids. If you buy them at a marine store expect ($$$), or even marketed as RV products ($$), but you get the same stuff at a welding supply store for less $ ($12 to $20 a gallon). Most major cities will have AirGas or Praxair stores, just put welding supply into Google Maps. Just tell the sales person you want to clean bare aluminum... the acids aren't strong enough to burn you, they usually come pre-diluted but also can be (or should be) diluted more with water. On a big mast, buy the $10 2 gallon size garden sprayer at HD or Lowes. Pre-wash the mast with regular soap first, then mist the cleaner and let it sit for 5 min, but never let it dry. Scotch brite pads do wonders. Rinse well, repeat if needed. Helps to be in cooler weather or not in direct sunlight.
I typically use a phosphoric acid solution which is a general de-scaler/degreaser for steel and stainless steel, but it also works for aluminum. If I was doing a big mast, I'd be getting the aluminum specific acid vs. the all purpose acid I just mentioned.
I typically use a phosphoric acid solution which is a general de-scaler/degreaser for steel and stainless steel, but it also works for aluminum. If I was doing a big mast, I'd be getting the aluminum specific acid vs. the all purpose acid I just mentioned.
@CloudDiver With the Aluminum Acid you will get a bright shiny aluminum mast, I think.
What happens with time after the cleaning and washing is done and the mast is returned to the boat?
What happens with time after the cleaning and washing is done and the mast is returned to the boat?
Essentially the same thing that happens with a new aluminum spar. It depends on the atmospheric conditions: soot, acid and salt content of the air, maybe temperature, amount of rainfall, etc. If the issue is "black streaks", then those are clearly abated. If the issue is relative "dullness", then that's an evolving thing. Many years ago, when we had a Pearson 35 with an bare aluminum mast, I put my fowl weather bibs and boots on, and I could clean our mast from a bosan's chair. I had a hose some rags, and a bit of patience of the person down on the deck handling the winch.
I would think that you'd be several years before you'd be cleaning the spar again.
I would think that you'd be several years before you'd be cleaning the spar again.
Yes, you would get clean and bright, but not to the point of looking polished. Here's the thing, and expanding on what @SG also commented; All metals oxidize. In the case of ferrous alloys (high carbon steel, stainless steel, etc) this oxidation is RUST. Aluminum and even Titanium also oxidize but visually it is much different. Aluminum forms a very thin layer of oxidation that almost transparent, as does titanium but Ti does it much slower so it almost never appears to happen. With aluminum you WANT that thin layer of oxidation, it actually protects the metal. This is very similar to copper roofs on buildings... they go green (or blue/green) over time and you don't rush up there and polish the roof, no way! That layer of copper oxide protects the underlying copper sheet for decades. Same with bronze... Some people will clean and polish off that beautiful brownish/green/blue patina and polish the bronze bright again. Although it looks nice, it is only temporary and does the underlying bronze no favors, plus it is very difficult to keep up with! Marine Bronze is so thick you really aren't causing harm, but in reality multiple cleanings of the patina are actually allowing the bronze surface to erode away faster than if you were to just let patina and leave it be.
For spars, the acid cleaners specifically for aluminum will take that layer of oxidation off so that you can clean ALL of the aluminum effectively. Eventually that aluminum oxide layer will form again and the appearance of the spar will 'dull' out. The rockwell hardness of the aluminum oxide is also much harder than the underlying substrate. Cleaning with acids like this on a regular basis would be a bad thing for something made of aluminum that is regularly exposed to the weather, especially if it were thin. For spars, you aren't doing it very often at all and the aluminum is very thick (by comparison to the mils thickness of the Al oxide), so there is no harm in doing this every few years.
I have cleaned anodized spars with phosphoric acid, and like I said this a 'generic' de-scaler/cleaner and not specifically for aluminum. It is effective, but maybe not as much as aluminum specific acids. Before I clean a spar that is anodized with that product I would be checking the chemistry of the acid and talking to the manufacturer to make sure it won't destroy the anodize. For bare aluminum, there should be no hesitation.
I have a 1979 Hunter 27. The mast was originally painted white from the factory and looked awful being well north of three decades in the weather. I painted mine, only because it was already. I called the folks at Interlux to get their advise. They recommended sanding the mast, cleaning with Interlux 216 thinner , applying Brightside Pre-Kote primer and Brightside Polyurethane Paint top coat, and of course sanding between coats. The thinner is also used to cut the paint for brushing on vs. spray. I experimented a bit before doing the mast and ended up brushing it on. You can’t tell it was brushed on, it flowed out very well. I had to fight my impatience all the way to not apply it too thick. I do have a few small runs, but you’ll never see them. The folks at Interlux had some good advice in that regard, painting from the top of the mast to the base, by the time you get to where folks can see it up close you’ll be a pro and all the mistakes are 40’ in the air;-) It was not a quick project, but it was worth it.
If you decide to paint, and you’re starting off with bare metal, you’ll also have to etch and apply a zinc chromate primer. I would have preferred an anodized aluminum mast, that would have saved me quite a bit of work. Then again, my mast was the envy of the dock when we splashed this past spring.
The photo was taken this past April, just after stepping and splashing. Would have been nice to let it sit and harden a few more weeks, but wanted to get out and sail. It’s none the worse for the wear, still looked great when we hauled out at the end of October. Also rewired, replaced the lights with new LED fixtures, new weathervane, lazy jacks, halyards and some of the standing rigging.
At 38 years it needed it!
If you decide to paint, and you’re starting off with bare metal, you’ll also have to etch and apply a zinc chromate primer. I would have preferred an anodized aluminum mast, that would have saved me quite a bit of work. Then again, my mast was the envy of the dock when we splashed this past spring.
The photo was taken this past April, just after stepping and splashing. Would have been nice to let it sit and harden a few more weeks, but wanted to get out and sail. It’s none the worse for the wear, still looked great when we hauled out at the end of October. Also rewired, replaced the lights with new LED fixtures, new weathervane, lazy jacks, halyards and some of the standing rigging.
At 38 years it needed it!