Chrome versus Nickel coating

[TJK1]

I need to design a shiney looking wear surface. A 6" square, 3 pound aluminum chassis will slide over it about 10 times per day. If the wear surface was steel, would chrome or nickel be a better durable coating to put over it?

If the wear surface was stainless steel, would chrome or nickel be a better durable coating for it?

 

[EngineerTex]

What I know about plating is from the hydraulic cylinders that I have used in the past.

1) I can't think of a reason that the substrate would make a difference. On the rare occasions that I have used stainless steel with a chrome plating, it has been to prevent corrosion of the un-plated portions.

2) It appears that your project requires an aesthetic quality. You stated that you need a "shiney looking wear surface." Speak directly with your vendor and ask to have a look at some final parts to make sure that it's shiny enough for what you're looking for.

3) In the industry, a "hard chrome" surface is not the same as a chrome-plated surface. A chrome-plated surface is not as hard or wear-resistant as a hard-chrome surface. The hard-chrome surface is probably what you're looking for, but what may be an issue for you is that although it is pretty shiny when polished, it is not going to be as shiny as the bumpers on your dad's '58 Buick.

4) The problem that you're probably going to run into on this is that dirt, grit and contaminants will get between the sliding surfaces and start to scratch off the coating, even though you're talking about an incredibly small surface pressure (0.08 psi). With that in mind, I don't think this is really going to be an issue of trying to decide what type of plating you're going to use. You might consider using a lacquer coating on top of it and go with the assumption that the lacquer will wear off and require replacement from time to time. Will your setup be lubricated? Can you put a wear pad under the aluminum block? If you use Nylatron (Nylon impregnated with molybdenum disulfide as a lubricant, cheap and readily available everywhere), I doubt you would ever have to worry about any wear at all.

5) All that being said, what you're talking about is a matter of simple hardness, i.e., which finished surface is harder? There may be a nickel surface treatment that can come close to the hardness of a hard-chrome plating, but I don't know of it. If you're looking for just the hardest surface you can get, go with a 0.005 - 0.010 in. thick hard chrome plating. You're probably not going to get much harder unless you go for a tungsten carbide plasma spray, ground, honed and lapped.

 

[coatingengineer]

Hi.

Perhaps you should review mechanics, first. For instance, what pressures are involved? What velocity and distance of displacement?

How does your base metal perform without surface treatment? What's the wear mechanism?

Understand these concepts and your choice will become a whole lot easier.

If you'd like more help, just see:

<a href="

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/Plating.html">Plating</a>

William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[Cockroach]

You may need to look at Ball or Gate Valve technology. Typicaly the flash of electroless nickel is 0.0005/0.0010 inches thick after degreasing and pickel of the component. The trick is to bake the part for three hours at 800F or so to get the free hydrogen out of the system from the acid process.

The expectation of HRc 55-60 hardness are typical results with very good adhesion and coat uniformity. The valve lasts for years in harsh environment and applications where abrasion are non-issues.

In the old days, chrome was flashed over nickel for wear resistance purposes. You do see it on occasion, but the practice faded in the late 1960's being replaced with better coating practices.

You may wish to look into the subject further with on websites dedicated to coating applications to the valve industry. Again, buzz word for seach is "electroless nickel coating" or "Flash ENC". Good luck with the research.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada