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ENGINE COATINGS - A REFERENCE THREAD

General engine tech -- Drag Racing to Circle Track

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Torquemonster

ENGINE COATINGS - A REFERENCE THREAD

Post by Torquemonster » Sun May 01, 2005 6:01 pm

There is so much confusion it appears out there amongst engine builders and those that want to build the best engine they can - about coatings.

Coatings for engine parts generally - ceramic coatings, friction reducing coatings, heat transfer coatings etc ranging from piston crowns to valve springs and bearings.

There are two schools of thought - and adding to the confusion is the fact that there will be good products and good operators in the coatings industry and bad ones - and therefore is a bad reputation the fault of the technology or the applicator?

1 - coatings are just not worth it. They peel off, flake off, or in the case of pistons - while reducing thermal transfer into the piston for a time - eventually they heat soak and under high cylinder temperatures actually compound the problem and cause premature piston failure - lading to a complete piston collapse.

The piston collapse/failure reputation re piston coatings specifically has been around since coatings first came out a decade or more ago but this reputation has stuck.

2 - the right coatings, applied by a good operator - is a genuine racing edge used by the best teams from Drag Racing to NASCAR to Formula One and in every category of motorsport where engine builders are looking for an advantage.... and for top street engines.

Personally I have used coatings to good effect and never had a problem, but my experience has been limited to ceramic piston crown coating, piston skirt teflon coating and ceramic coatings on chamber and valves.

It would be a wonderful resource reference if race engine builders or those with inside knowledge on what works and what does not would share some of their experience here so that in time - the coating industry either dies a natural death - or becomes maintstream if it deserves to - and this will lead to new technologies to spearhead the fringe of power hunting and reliability.

I'll start with my own opinion - which is limited and therefore could be wrong:

I believe that the modern ceramic coatings as used on bearings, valve springs, piston crowns, chambers and valves, and the friction reducing coatings on pistons skirts all help create an engine that runs smoother, cooler, and maintains more power in the chamber, increasing component life and improving resistence to detonation.

Discuss and if agreed - who have you found does a good job?

If disagreed - was yours a bad experience and could it have been bad application or inferior product?

I have no vested interest either way - this is for a better understanding of a fringe technology where we all gain.

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Post by gofaster » Sun May 01, 2005 7:04 pm

My only personal experience with coatings has been with the skirt coating that Harley Davidson uses on their pistons and Nitrided and Melonite coated valves. In both cases the coatings appear to help reduce scuffing and galling with no problems. Newer Harley pistons are being fitted at 0.0005 to 0.00075 (Yep, less than a thou) and living long and happy lives in street engines.
Nitrided and Melonite valves look the same to me, maybe it'stwo different names for the same thing depending on the supplier.
Speed talk has an interview with the people from JE pistons, and they have some very interesting things to say about crown coatings.

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Post by Shaun » Mon May 02, 2005 11:56 am

In a nutshell, what did the JE guys say about piston crown coatings?

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Post by phoenix » Mon May 02, 2005 3:11 pm

I don't know, what did they say?

Torquemonster

Post by Torquemonster » Tue May 03, 2005 1:34 am

Ross offer thermal barrier coatings (ceramic based I believe) and anti-friction skirt coatings as an option on their forgings and highly recommend them for boosted and nitrous applications.

Subaru now provide them on all their turbo engines - although they are not the only OEM to do so I believe, they are the one I know by name.

Swain Coatings boast some pretty big motorsport names as customers, and virtually every top 10 engine builder for the last 2 years used at least some coatings whether bearings or valve springs or pistons etc in the annual Popular Hot Rodding engine builders contest.

ok - let's keep this going :)

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Post by gofaster » Tue May 03, 2005 3:30 am

The people at JE described piston crown coatings as "purple smoke and mirrors". They say the application methods anneal the piston crown sometimes as low as single digits, Rockwell.
They had good things to say about anti-friction skirt coatings, and ring groove anodizing.
You asked and and I am just passing on what they said.

Torquemonster

Post by Torquemonster » Tue May 03, 2005 5:32 pm

That is important info GoFaster - the problem highlights the importance of differentiating the good from the bad.

The trouble is 99% of us tend throw the baby out with the bath water until something is proven so well it is already verging on mainstream. By then - what edge can you expect because everyone else is doing it anyway?

JE are saying it is ALL smoke and mirrors re thermal barrier coatings on the crown while Ross are recommending it. From what I understand virtually ALL Top Fuel engines run coatings - and no engine has to tolerate as much stress on the piston as those engines... they are running on the verge of hydraulicing from massive fuel loads the whole race.

We need some real data to be able to tell the good from the bad.

Assuming now that certain application methods anneal the piston crown into a weaker product requires identifying which methods and products are causing this - and then discovering which are not.

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Post by ChrisU » Tue May 03, 2005 6:07 pm

I find it very interesting, the LACK of input on coatings, from those whom are very experienced in this area.... 8)

My experience lately leads me to believe it's for good reason. I'm having troubles keeping coatings on piston tops, combustion chambers and valve faces from a very prominant company.... which will be un-named until I speak with them about it first.
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Torquemonster

Post by Torquemonster » Wed May 04, 2005 8:18 pm

Thanks Chris - that is the kind of info we need.

I have also invited Swain to come here and post as they are one company that is supposed to have dones some R & D innovation in this field... there are others.

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Coatings

Post by hotrod » Wed May 04, 2005 10:07 pm

The four big players I am aware of in the specialty coatings field are:


HPC ---- http://www.hpcoatings.com/
Jet hot ----- http://www.jet-hot.com/
Swain Tech ----- http://www.swaintech.com/
Tech line Coatings ---- http://www.techlinecoatings.com/

It is interesting that all of these manufactures mention that the coatings they use, were spin offs from NASA and aerospace application developments. You may find better technical information on coatings and their performance in aerospace journals, and reports, rather than in the automotive press.


In the case of Techline, they sell their product line to a large number of small powdercoating jobbers, so one issue is the attention to detail at your particular vendor.

They do make the following points in one of their online FAQ's

==================
Surface Prep:

* Parts first must be sandblasted at low pressure (40 psi using a suction type blaster) using fine sand (120 grit aluminum oxide is recommended), NOT with glass bead. Then the part should be degreased using acetone, lacquer thinner, M.E.K. or similar non petroleum based solvent that leaves no residue. The coatings should be applied with an airbrush or detail touchup gun. Baking may be accomplished with any oven. Kitchen ovens or even toaster ovens work just fine. Obviously the size of the oven will determine how large a part can be coated and cured.

# DOES IT MATTER HOW THICK I PUT THE COATINGS ON?

* YES, the coatings are thickness sensitive. Generally .0015" is the maximum thickness recommended. This thickness will be achieved when a solid color is seen. Putting any coating on too thick can cause the coating to crack, flake or bubble up.


# CAN I USE GLASS BEAD TO CLEAN MY PARTS?

* No: only use fine sand or fine aluminum oxide. Glass bead is round and while it is a good cleaner it closes the pores of the metal. Use fine sand/aluminum oxide which etches the metal and cleans/opens the pores allowing the coatings to bond into the metal.
===============

Some of these coatings require baking at temps in the 450 - 500 degree range which can modify hardness even on steel components so I can easily see where the same might apply to aluminum pistons.

Techline gives lots of technical info on their site for their specific coatings. Since they sell through vendors they also have application guidelines, and some news letter items, that as seen above, lead me to think the application process and surface prep are as important to the success of the coating as the brand/type of coating.

I suspect that many of the problems with chipping flaking coatings would turn out to be traceable to over thick application or lack of or improper surface prep and curing.

I have limited experience with the coatings having only used some of the techline products in a do it yourself application. But they seemed to work okay for my application ( exhaust system coated with their black satin ).

Larry

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Post by ChrisU » Thu May 05, 2005 6:34 am

To be honest I've had better luck with the do-it-yourself water based Tech Line coatings, than the professional stuff..... so far.
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Joe Shober

Post by Joe Shober » Thu May 05, 2005 3:02 pm

We get our stuff coated at Dart we are about to run it so I guess wewill see soon how it holds up. I also want to bring this point up, JESEL coats all there lifters and they all hold up great. When I was at Dart and was walked thru the plant and they explaned how much of a process it is to clean and prep the parts its no wonder people have problems with coatings.

Torquemonster

Post by Torquemonster » Thu May 05, 2005 4:49 pm

Thanks to the people who have shared something so far. It is early days but there appears a pattern emerging that the problem is not technology related but the integrity of preparation... although it is certain not all coatings are created equally.

Despite the fact coatings have been around for decades to evolve to where they are now - there remain few top quality engine builders that use coatings extensively in their top racing engines and endurance engines - willing to talk about it....

i's a bit like cyrogenic treatments... there's a lot of doubt and confusion over it - but a few quietly know where to go and get great results...

I started this thread because I feel coatings have been around long enough they should be out in the open - but people need guidance on who they can trust to do it right - and who is unreliable.

Money spent well here can really make a noticable difference. Money spent wrongly can cost an engine. It's a shame the subject remains under a cloud with those odds.

Where's those that know they are onto a good thing? :wink:

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Post by SStrokerAce » Thu May 05, 2005 8:20 pm

We might as well get into cryo treating as well on this...

Understanding why it works is one thing but the big claims some people have made suprise me....

Anywas to quote OldSStroker from another forum:

"Thoughts:

One of the primary advantages of sub-zero treatment, whether it be -120F or -300F is the conversion of retained austenite to martensite in the steel (or ductile iron) structure. Without getting too boring, a nearly 100% martensitic structure is preferred for strength over one with some untransformed austenite which occurs during heat treating. If there is 1-3% or so retained austenite, there won't be much gain, but if there were 2-3 time as much, you might expect more gains. We'll know more about LS1 cranks soon.

Anytime you cool or heat metal parts, especially over a 600F range, you may change size or configuration. I worry most about straightness of things like cranks and cams during post-machining heat treating.

Engine parts are not tool bits. The material, function and heat treatment are very different.

Before I'd cryo treat a block, I'd want to know how the cylinder bore structure and hardness changed because different structures require different surface conditions for best ring seal. What works for a normal gray cast iron isn't necessarily optimum for cylinder liners which were made and heat treated differently. I suspect the same thing with treated blocks.

If I were building an endurance engine (Winston Cup, etc), I'd do extensive testing of treated and untreated parts before I treated any of them, then pick and choose what helped. If I were building a street engine, I would be sure that the treatment was helping rather than hurting before I'd use it. IMO, this is especially true with cast, or PM, and subsequently heat-treated engine parts like cranks and rods.

All that being said, some sub-zero (around -120F) treatment is regularly used when making many parts. We produce many bearing rollers, and impact parts from high carbon, high chrome bearing steel which are always sub-zero treated. This is done before the finish machining/grinding operations, however."


Thanks to the great minds who run LS1Tech.com the rest of that thread is lost in cyberspace....

On the topic of coatings.... I agree with Chris on this

"I find it very interesting, the LACK of input on coatings, from those whom are very experienced in this area.... "

Bret

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Coatings

Post by Leonard » Fri May 06, 2005 12:11 pm

I was just directed to this site. I am the President of Tech Line Coatings, Inc and the chief formulator for the company. I hope that my contributions will be of benefit to those interested in this subject.

In reading the mesages I can see that in general the information is correct. Coatings work and work extremely well when;

The proper coatings is chosen
The proper prep is done
The coating is properly applied.

Unfortunately a great deal of old information as well as innaccurate information circulates in regards to the subject of coatings. In the past coatings were introduced that did not live up to their billing, this damaged their reputation even though it has been nearly 20 years since this first occured. In other cases misunderstandings have occured that confuse the issue.

One example has to do with combustion chamber coatings. They DO NOT create more heat in the chamber. They simply maintain the heat generated by the combustion process longer through the power stroke, by reducing the amount of heat that is lost through conduction, into the parts exposed to the heat. It is true that by making tuning changes, allowed by the use of coatings, one can now increase combustion chamber temperatures, providing more power, but since the surfaces are coated this additional heat poses no problem as the actual part temperature will be lower than in an uncoated engine.

I will be happy to answer any questions that forum members may have on this subject. Since I will be leaving for a business trip to Europe on May 11 and will not return until May 31, I will not be able to address questions for more than a few days.

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