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Painted mine with two part PPG to fade from black to silver. If I was a better painter I might have been able to smooth the transitions more but it still looks pretty good out in the daylight. This might work even if your body color is different.
GM painted them in the later 70's C3's. 68 & 69 panels were fiberglass. '70 and up were anodized aluminum.
Yes, you can paint them. But, you do NOT want to sand them to prep for paint. The anodized layer is for part strength and surface durability to withstand road-rash. Just use #0000 steel wool to buff the surface smooth, clean with lacquer thinner or other volatile cleaner, then prime and shoot.
First, you need to strip (not sand) off the anodized surface. This surface makes the piece more shiny and harder, preventing many scratches and protecting against corrosion. It also seals the surface and eliminates the "tooth" that paint needs to adhere strongly.
To strip the surface, you'll need something caustic. I used a sodium hydroxide product from Eastwood (they don't seem to offer it anymore), but anything containing lye (such as drain cleaner or easy-off) will do the job. Whatever you use, I suggest you dilute it - it will give you better control of the process (though it will take longer) and it will be safer (fumes and chemical burns). Neutralize everything with lots of water.
Next, wet sand the surface with 400 or 600 paper. If there are dents or dings in the piece, now is the time to fill them (I used JR's epoxy).
Finally, paint them. I used a 2K primer and then another 2K top coat (black).
Unfortunately, that will get you a nice, clean & shiny rocker panel which is ready to paint....but which will not hold up to road junk in the future. Any small rock it encounters will put a nice dent in the part, instead of just scratching the paint. Your advice is sound.....with regards to painting the part. But, in the long run, stripping the anodized layer is not a good thing to do.
Unfortunately, that will get you a nice, clean & shiny rocker panel which is ready to paint....but which will not hold up to road junk in the future. Any small rock it encounters will put a nice dent in the part, instead of just scratching the paint. Your advice is sound.....with regards to painting the part. But, in the long run, stripping the anodized layer is not a good thing to do.
Anodizing aluminum does NOT increase the mechanical strength of the anodized object. It is a surface treatment, a controlled oxidation of the surface to provide a hard smooth outer surface to protect the surface from environmental oxidation (preserving its appearance) and from scratches and scuffing. The anodized layer is microscopically thin, and the removal of this layer in a controlled chemical fashion does not appreciably change either the gauge or temper of the substrate. In a rocker panel in service, you will get exactly the same number of dents and dings, of the same magnitude, in an anodized and un anodized one. The difference between the two will show up in appearance. The unanodized piece will show surface insults - scuffs, corrosion and surface scrapes - much more readily than the anodized piece.
C 3's anodized rocker panels do pick up dings in service. If you look at them under magnification you will see they appear cloudy, and for larger dents you can see a web of small cracks. This is where the hard outer anodized surface was unable to conform to the deformation of the substrate. Stripping off the anodization allows you to fill these unsightly areas and to paint the rocker panels to restore appearance. Modern paints are very hard and tough and perform well in this area, but will occasionally require touchup or repainting - you cannot repair the stock anodization.
I don’t have painted rocker panels, but I have been driving my car for the last 15yrs or so with rocker panels that have no anodizing. I don’t care for the look of them anodized, so I had a local chrome shop remove the anodizing and polish them for me. I drive my car a lot, and I am happy to report that removing the anodizing has had no negative consequences to the structural integrity or the aesthetics of the rocker panels.
I take it that you have never actually removed that anodized layer to find out how flimsy that solf aluminum panel actually becomes. I have (much to my disappointment).
I take it that you have never actually removed that anodized layer to find out how flimsy that solf aluminum panel actually becomes. I have (much to my disappointment).
You are quite incorrect. In this thread I described the method I used to remove the anodization and the method I used to paint them. I am quite satisfied with the result.
Perhaps you would like to enlighten us about your experiences with non-anodized rockers, or more broadly with non-anodized aluminum that substantiate your repeated assertions about the loss of strength caused by deanodization.
You (and anyone else who is interested) may want to peruse the following info about hardcoat anodizing and its properties. Anodized coating hardness is in the same range as chrome plating (very hard) and is meant to provide wear and damage resistance. The anodized layer is brittle, but the aluminum substrate provides support to keep it intact. In exchange, the hardcoat provides sturdiness to the soft aluminum.
Having removed the hardcoat during a "brain fart" [in an attempt to make it 'purtier'], I was amazed that I could no longer lift the rocker panel in a horizontal position without it drooping significantly. That easily convinced me that the anodized layer provided a lot of resistance to bending, as well as to surface durability.
You (and anyone else who is interested) may want to peruse the following info about hardcoat anodizing and its properties. Anodized coating hardness is in the same range as chrome plating (very hard) and is meant to provide wear and damage resistance. The anodized layer is brittle, but the aluminum substrate provides support to keep it intact. In exchange, the hardcoat provides sturdiness to the soft aluminum.
Having removed the hardcoat during a "brain fart" [in an attempt to make it 'purtier'], I was amazed that I could no longer lift the rocker panel in a horizontal position without it drooping significantly. That easily convinced me that the anodized layer provided a lot of resistance to bending, as well as to surface durability.
My experience with HARD COAT (type III in your citation above) anodizing is extensive (I made almost all of the pans in use by pizza hut, for instance). I know the differences between hard coat (type III) and other decorative (type I) and environmental anodized coatings. I agree with much information about type III hard coat anodization - It is VERY hard and will protect the surface of the much softer substrate. It is also an expensive and time consuming process and is much less frequently used than type I decorative anodization.
Decorative anodization is an entirely different process than hard coat. has much thinner film thicknesses and is used when you want the aluminum substrate to appear chrome like. This is the process that is used on C3 aluminum rocker panels. As quoted from your cite,
"Does anodizing make aluminum stronger?
Aluminum is used in industry because it has a good strength-to-weight ratio. ... However, aluminum isn't a very hard metal and can be scratched fairly easily. Ceramics (oxides) are much harder than most metals, so to improve the scratch resistance of aluminum, “anodization” is used to thicken the oxide layer"
In other words, as mentioned in my previous post, the anodization of this part will improve appearance and provide some surface protection against scuffs, scratches and small dings. However, it will not improve the mechanical strength of the piece anymore than a coat of paint would improve its strength
Interesting... but I believe the hardcoat applied is NOT the decorative type. GM would not have spent ANY money on anodizing for 'appearance' purposes. They would have painted the part, if it needed to be "more purty", as it would have cost less and been simpler to process. They hardcoated the part for durability and strength. primarily to resist road rash (which is does well WITH the anodized layer in place).
As old man Ripley used to say..... "Believe it or Not!!"
On my 79, I used 0000 steel wool and smoothed them down, and then painted with Krylon 1613, 13 years ago and after about 30000 miles, they still look great.
strip/sand off old paint, use an etching primer for aluminum, then a primer, then a 2 part black/color. Go to a local autopaint store and let them know what you are working with. The 2 part color can needs to be used in a few hours. Or you could go enamel like rustoleum and just do a few coats of that.
I just cleaned mine up with steel wool, 0000 I believe, taped off the recessed line and painted them with a rattle can. Actually held up quite well over the years.Like someone had mentioned they really don't get beat up from much road debris.
Sorry to rekindle an old thread, but I have a question. My 72 rockers are pretty well scratched and I don't want to paint them. I like the aluminum look. I have to sand out the scratches thus removing the anodize coating. If I were to sand, clean and buff to a shiny new surface, would it be beneficial to ceramic coat them. I know its not a hard as anodizing, but better than just wax. Thoughts?
How about powder coating?
05-30-2019, 05:16 PM
