anyone familier with this process. it has come up in a conversation i was having about coatings. This is or my BBC blown engine i am working on. i hate to take more time and money but if it is something that will really help...

I use ceramic barrier coating on all my supercharged engines, but not sure what benefit hard anodizing would have as compared to the barrier coatings.

Jody

I have a rod/piston clock sitting here on my desk which I bought at Race Rock. It's an actual rod/piston out of John Force's nitro funny car. I'm 99% certain the piston is hard anodize coated. So if anything, it does go to show that the process is used on pistons.

On the pistons in my engine, I had the skirts dry film coated for reduced friction and the domes are thermal/ceramic coated.

I've heard of hard anodizing the ring lands in severe-duty apps, but not the entire skirts. Usually the skirts are dry-film moly coated. I am a firm believer in ceramic barrier coating the dome and dry-film coating the skirts. Doesn't mean you can't hard anodize the entire skirts... if anyone has hard info, please chime in!

Troy

Well, the piston I have sitting here is an olive drab green color inside and out. 100% of the piston is coated/hard anodized.

It's a surface hardening process for AL. and has corrosion inhibitive properties.
In other sports, it is done to high wear areas to get them to last longer.
IIRC, you have to dip the part in a chemical solution.
So it would be hard to do a small section.
The land only thing is probably a misstatement perpetuated by magazines having head placement issues. No offense Troy, I didn't put much thought into it till you said it.
Cause I read it a while back too and have been thinking about it having it done.

Top Fuel pistons manufactured by JE (and possibly others as well) are the olive drab color, as mentioned in one of the previous posts. Am not real sure what the process is, but doubt that is is necessary in a gasoline engine. A good set of forged pistons with possibly a coating on the skirts should last a lifetime in a properly tuned and maintained race engine. Note the emphasis on PROPERLY!
Many NASCAR engine builders are now using billet pistons. These units are 100% CNC machined, then hand finished by expert craftsmen and VERY expensive.

As far as high strength grooves are concerned, many heavy duty pistons (Cummins, Cat, etc) have a steel groove in the pistons. The steel grooves are placed in the cast pistons and are much stronger than grooves machined into the piston material. These are necesssary in diesel engines, aka 'controlled detonation' powerplants.

I knew I'd seen green ones somewhere. Just couldn't place it last night.
My machinist had one laying around. They are used in the lower fuel classes also.
Not just TF.

I would be concerned about the accuracy of the application of any kind of coating or anodizing for the ring lands. High performance engine builders spend a lot of time and money (just compare the cost of diamond finished rings to standard rings) to insure that the clearance between the rings and the lands is minimal and consistent in order to maximize ring seal. If you have to go back and re-machine the lands after these applications (to insure the proper clearances), it is extra cost and may even remove some of the coating/anodizing that you just applied.

Fwiw, there are diesel pistons made like a "knife and fork", with a steel deck and ring land containing top and aluminum skirts for quiet operation!!

The pin holds the two parts together if not mistaken.

pdq67

I would be concerned about the accuracy of the application of any kind of coating or anodizing for the ring lands. High performance engine builders spend a lot of time and money (just compare the cost of diamond finished rings to standard rings) to insure that the clearance between the rings and the lands is minimal and consistent in order to maximize ring seal. If you have to go back and re-machine the lands after these applications (to insure the proper clearances), it is extra cost and may even remove some of the coating/anodizing that you just applied.

You don't have to re machine your crankshaft when you get it heat treated do you?

Same idea, anodizing is a surface treatment. Not a coating. It would be one of the last things done to the piston.

You don't have to re machine your crankshaft when you get it heat treated do you?...If the tolerances for my crank were as tight as the tolerances on my ring lands, I'd give it some serious thought. Along the same lines, my ring and piston manufacturers both recommended against cryogenically treating my pistons due to concerns about ring land tolerances.

I
The land only thing is probably a misstatement perpetuated by magazines having head placement issues. No offense Troy, I didn't put much thought into it till you said it.
Cause I read it a while back too and have been thinking about it having it done.

None taken, however several vendors offer pistons with hard anodized ring grooves to aid in preventing the rings "welding" to the pistons under extreme use conditions. I've seen this advertised more for hi-po Import applications than domestic stuff. That's what I was referring to. I have yet to see an "off the shelf" completely hard anodized piston, but that doesn't mean they aren't out there.

If you want to get into really bizarre stuff, several new Mercedes engines are using iron-plated pistons riding in aluminum bores (which I believe are Nikasil coated.) I don't know how the iron plating is adhering (and remaining adhered) to the aluminum pistons given the gross CTE mismatch between the two materials.

Roger has hit the nail on the head. As with most high performance parts sourcing, your best bet it to chose a manufacturer who you trust emphatically to be capable of producing the very best product. Then contact that manufacturers technical or sales department and have them assist you in picking the best part for your combination. THEN use these parts exactly as they are engineered and produced.
Most high-quality racing pistons (JE, CP, Bill Miller, Wiseco, etc) are available with ring land dimensional tolerances in the neighborhood of +/- one half tenth. That is .00005" which in real world measurement is about 1/60th the thickness of a human hair (even a red one). At this time, it is not possible to manufacture rings with that narrow of a tolerance range (regardless of what you see advertised), but it is nice to know that the piston grooves are that close.

BTW, the two piece piston that pdq67 refers to is called a "cross head" piston and it has been used in Detroit Diesel engines for many years.