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August 27, 2026 4 min read
I recently posted a video showing how I use automotive clear coat to keep bare aluminum engine parts from oxidizing. If you haven't seen the original, check out How to Keep Bare Aluminum Looking New During a Restoration to see the process I use.
The comments came quickly.
People said the clear would peel. It would yellow. It would trap oxidation underneath. Some even said clear coating an alternator would cause problems.
I could argue about it, but there's a much better answer sitting under the hood of my 1966 Impala.
I clear coated the aluminum intake manifold and water pump on this car in 1999.
Twenty-seven years later, they're still on the car.
Here's how they held up.
When I coated these parts in 1999, I wasn't conducting an experiment for a future article or video. I was simply trying to preserve the clean appearance of the cast aluminum.
The intake manifold and water pump have now spent nearly three decades in a real engine compartment.
They've been exposed to engine heat, temperature cycles, moisture, dirt and normal use.
And the clear coat is still there.
More importantly, the aluminum underneath still looks good.
That's why I wanted to make this follow-up. We don't have to speculate about whether clear coat might work over the long term.
We can look at a set of parts that have actually been coated for 27 years.
This was one of the biggest concerns people raised.
Take a look at the intake.
After 27 years, it hasn't turned into the yellow, discolored mess people warned about.
Does it look exactly like a freshly coated part sitting on a workbench?
No.
It's been installed on a running engine for nearly three decades. I wouldn't expect it to.
But the clear has done exactly what I wanted it to do: preserve the natural appearance of the aluminum and prevent the heavy, chalky oxidation you normally see on unprotected cast aluminum.
No widespread peeling.
That's important because adhesion is one of the reasons I generally prefer this technique on cast aluminum.
Cast aluminum has some natural surface texture. That gives the coating some tooth to grab onto.
Surface preparation still matters, of course. You can't coat a contaminated, greasy surface and expect great results.
But properly prepared cast aluminum can hold clear coat extremely well.
My intake manifold is proof of that.
Another common argument is that clear coat will trap moisture and cause the aluminum to oxidize underneath.
A failed coating certainly can allow moisture underneath it.
That's different from saying clear coat causes oxidation.
The whole purpose of the coating is to create a barrier between the aluminum and the environment.
If the aluminum is properly cleaned and prepared before coating and the clear maintains adhesion, that barrier helps keep moisture, grime and other contaminants away from the metal.
After 27 years, I'm not seeing the catastrophic oxidation underneath the finish that some people predicted.
This one generated some interesting comments.
The alternator on the Impala was also clear coated, although it's much newer than the intake and water pump. I coated it approximately three years ago.
It's still working just fine.
There's an important distinction here.
I'm coating the exterior cast aluminum housing. I'm not spraying clear coat indiscriminately into bearings, electrical connections, grounding surfaces or openings.
Those areas need to be protected and masked appropriately.
We're preserving the aluminum housing, not dipping the entire alternator in clear.
The fact that these parts survived 27 years doesn't mean you can grab any clear coat, spray it over dirty aluminum and expect the same result.
Preparation and application matter.
I use automotive clear and apply it correctly to properly prepared aluminum.
I covered that process separately in my guide How to Keep Bare Aluminum Looking New During a Restoration.
That's where I explain the preparation, light coats, flash time, curing and the areas that should be masked.
This article is about something different:
What happens years after you do it.
And now we have a pretty good answer.
No.
I wouldn't make a blanket statement that every aluminum component on a vehicle should be clear coated.
Extremely high-temperature components are a different situation. Machined surfaces, gasket surfaces, threads, grounding points and certain electrical areas shouldn't simply be covered in clear.
The technique has to make sense for the component.
Where I've found it particularly useful is on visible cast aluminum engine components where I want to preserve that clean, natural aluminum appearance.
That includes parts like intake manifolds, water pumps, accessory brackets and housings.
Absolutely.
In fact, I still do.
That's probably the most meaningful conclusion from this entire experiment.
If I had clear coated these parts in 1999 and watched the finish fail a few years later, I wouldn't still be using the technique today.
Instead, I can open the hood of my Impala and look at parts I coated nearly three decades ago.
For me, that's enough evidence.
There are endless debates in the automotive world about what works and what doesn't.
Some of them can go on forever because everybody has an opinion.
One advantage of having worked on cars for a long time is that eventually you don't have to rely on opinions.
You get to see the results.
I clear coated this intake manifold and water pump in 1999.
Twenty-seven years later, they're still on the engine and the aluminum still looks good.
The proof is in the pudding.
Want to know exactly how I prepare and clear coat bare aluminum parts?
Read my How to Keep Bare Aluminum Looking New During a Restoration guide for the complete process.
Have you clear coated aluminum engine parts? Leave a comment below and tell me what you coated and how long it's been holding up.
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This site documents real builds, tools, and shop work from my own projects. Some pages are showcases. Some are how-tos and tool reviews. If you’re working on a project and want experienced guidance, I offer one-on-one coaching.