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Need a high friction coating

Q. I am looking for a way to increase the friction coefficient of steel or stainless steel washers. The hardness of the parts is about 40Rc. My current parts have a coeff. of about 0.2 and I would like to increase this by as much as possible. 0.4 or 0.5 would be ideal.

Ideally, this will be a relatively low cost mass finishing process. Parts will range in diameter from about 0.50 to 3.00 in.

Is there a plating, surface treatment, or conversion coating that can be used to achieve high friction?

D George
- Cleveland, Ohio
September 30, 2022
Ed. note: This forum was built as a gathering place for sharing tips, pics, anecdotes, & opinions to promote camaraderie.
        When engagement is requested by strangers withholding their names, readers may be less likely to engage.

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⇩ Related postings, oldest first ⇩

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Q. I am looking for some material with high friction coefficient with some finishes metal surfaces like car bodies. Could you give me some suggestions? The material needs to be easy to find and low cost and hopefully can hold the friction well under wet conditions (say 60%+). How high the coefficient can go? (the higher the better). I am hoping somewhere higher than 0.5 under dry condition.

Thanks ahead!

Robert Yu
chemical machinery mfgr. - San Jose, California, USA
2003

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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Q. I need to increase the surface friction between a stack of stainless spacers. I am applying a compression force to the stack and relying on surface friction to hold them. I have called out a sand blast finish but this quickly became smooth and allowed the spacers to move. I also need to maintain a tolerance of .005 on the thickness of the spacers. Any suggestions for a repeatable finish specification?

George Fowler
designer - Jackson, Tennessee
September 14, 2009

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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High friction, durable coating needed for 6000 and 7000 series aluminum alloys

Q. I need some help finding a surface treatment for aluminum alloys (specifically 6061-T6 and 7075-T73) that will provide high friction at the contact surface of a bolted joint. I had several recommendations to look into plasma spray processes for applying tungsten carbide or ceramic powders, but these coatings don't appear to be very durable and are prone to chipping during handling (bumping things around when moving bolted assemblies into place).

Does anyone have a suggestion for a durable surface finish that will provide a consistent high friction value? I'm interested in chemical treatments that increase surface roughness, penetrating stable surface oxides like anodizing, deposited finishes like plasma spray...pretty much anything. I'd even be interested in mechanically prepared surfaces that provide high surface texture as long as the raised material won't crush under bolt pressure.

In order of preference these are the behaviors I'm interested in:
1. High Friction (above 0.3 dry static friction coefficient, higher preferred). Many published materials have a static coefficient higher than this but I've found them to be inaccurate.
2. Durability. The surface finish needs to hold up to normal wear and tear without cracking or flaking and generating particles. Normal wear and tear would be bolting and unbolting two parts about a half dozen times.
3. Corrosion resistance. Since I'm primarily interested in aluminum alloys, I need a minimum level of corrosion resistance. We typically use chemical conversion coating per MIL-DTL-5541 [on DLA] Class 3 to get a minimum level of protection.
4. Low porosity. I would prefer low porosity to make it easier to clean the surfaces and reduce drying time.
5. Solvent compatibility. At a minimum it needs to be cleanable with isopropyl alcohol. If stronger solvents like acetone ⇦ this on eBay or Amazon [affil links] Warning! highly Flammable! or MEK work then that's even better.

I know it's a tall order, but I'm hoping for some help :o). This is for a commercial aerospace application with a fairly high volume of work if a suitable finish is found.

Peter Cipollo
aerospace design engineer - Dulles, Virginia
February 17, 2010

I requested some additional information from ESK on their diamond/electroless nickel coating. That's exactly the type of coating I was looking for. If they can put it onto corrosion resistant steel instead of spring steel then it's an excellent match for what I'm looking for.

Thank you!

Peter Cipollo [returning]
aerospace - Dulles, Virginia, USA
March 1, 2010

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Q. Hello. My name is Mark. I'm a mechanical engineer for a plasma fusion research laboratory (government). I need a high friction coating for a stainless steel (316SS) to G10 bolted joint. The static coefficient of friction required is 0.5 or greater. This joint transmits high torque. The coating could be applied to either surface, but I'm assuming the stainless steel part will be coated. The average contact pressure is 25MPa. The operating environment is ambient air, room temperature, but all materials should be low in magnetic permeability (i.e. stainless steel).

Mark Smith
Design Engineer - Princeton, New Jersey
June 7, 2011