E85 and Coatings

[95z28]

Hello All

Looking for people who have been running E85 and using coated pistons.  We lost an engine this weekend.  We have been running E85 in it for four years.  When we tore it down all the piston skirt coatings had came off the pistons in flakes and clogged the oil rings.  Other than that and the resulting damage the engine was in good shape.

So the only thing we have is the engine has always been on E85.  The question is has anyone else had an issue like this.

We are not pointing fingers or blame and will be calling the piston manufacture monday.  We are just looking to see if anyone else has seen anything like this.  the coating came off suddenly and in flakes

[twistedz]

No one?

Piston manufacture said the fuel ate the coatings and oil break down is what whipped out the pistons.

One of them had .032 piston to wall clearance but did not break

[triplenickel]

I don't use coated pistons, so I cannot give any info on that. I have seen no oil related or unusual wear or problems in my 6 years of using E85. As far as the manufacturer's claim on the coatings, I'm not going to say that E85 didn't cause your problem, but I would expect the manufacturer would point to something other than themselves. Are you experiencing fuel dilution of your oil?

[David]

There are four factors that cause piston skirt coatings to fail in an ethanol environment
1 - Resin
2- Lubricious components
3 - Part prep prior to coating
4 - Solvent

A MAJOR piston manufacturer contacted me to hire me to fix this problem for them. I could not help them as I am working for a piston manufacturer already. In their case, their problem is #1 - Resin. I will elaborate on these four causes in a little more detail. If you would like to discuss this further, please feel free to call me at 520-227-2070 (David)

1 - Resin.
There are pretty much, two types of resins used in skirt coatings. One of the largest piston manufacturers in the world is using a phenolic resin, which just cannot withstand the corrosive nature of ethanol. Until they change their resin, they will not be able to resolve their issues. But, they own the coating manufacturing company, so they do not want to admit that their coating is inferior
A PAI resin is the best choice for many reasons, but in this case, definitely for its corrosion resistance

2 - Lubricious components
Almost every single piston manufacturer is using one and only one lubricious component...Graphite. This is the standard go-to component used in DOW D-10. On the good, better, best scale, it is "good". It is adequate, but there are MUCH better components that can withstand much higher loads, are more lubricious and will absolutely outperform DOW D-10 and other similar coatings.

3 - Part prep
Without a doubt this is the number one MOST important aspect of any surface treatment, of which piston skirt coating is not immune. This is an area that many many piston manufacturers overlook to minimize costs. They do so at their own peril. Not only in ethanol environments, you will see many piston manufacturers coatings fail due to the lack of proper part cleaning/preparation.

4 - Solvent
With PAI resins, you need a solvent to melt that plastic. NMP is the absolutely best solvent to use, but the EU banned its use do to the claims that it is a carcinogenic. As a result, DOW D-10 no longer uses NMP as its solvent, but they switched to a FAR inferior solvent...GBL. This stuff is BAD stuff, dangerous (Date rape drug), but most importantly to this particular discussion, it is HORRIBLE for coating adhesion. Even with a perfectly clean and prepped part, the new DOW D-10 is extremely finicky and difficult to get to properly adhere to the piston. The really bad news....nearly every pistons manufacturer is still using DOW D-10 on their pistons.