Coating Question

[ChipFuller]

At our plant we are refurbishing a mixer that we use to mix our propellent. Part of the reason of the refurbishment is because the paint is flaking off in some areas in particular this part the mixer carriage. We can't allow any paint flakes in our process. The mix bowl is slid into the mixer carriage and then bowl is lifted up with the carriage. A lot of paint has chipped and flaked off. We were originally going to fabricate a new carriage out of stainless steel but it's time prohibitive. Some people have suggested powder coating and some have suggested electroless nickel plating. Which would be good for this application? Does electroless nickel plating hold up to pieces being slid across it and being impacted?

Thanks

 

[alexit]

While powder coating is tougher than liquid paint, its still paint. The assembly you have may have been powder coated originally. Some plating holds up very well to sliding contact (most machine tools have hardened and hard-chrome plated guides) except if you distort the base material, then the plating comes off easily. I would suggest you inspect the assembly for any material deformation in the areas where the paint is coming off. If it looks intact then try the plating.

Alex

 

[ChipFuller]

This part is definitely painted and not powder coated. Which would be better hard-chrome plating or electroless nickel plating? This part is a mild steel weldment. Will the process warp it? What do you mean by distorting the material?

Thanks
Chip

 

[alexit]

If you have mushroomed the edges of the mild steel part, or dented the surfaces, or bent flanges by lifting the bowl into the carrige then you have distorted the material and any plating put there will flake off when this happens again.

"The plating process is not hot enough to warp parts"...I love when the supplier says that...I work with parts requiring 0.5 micron (20 millionths of inch) in size and geometry so I must re-grind after plating.

You should contact a source for plating and have them look at the parts. I find the chrome is nicer but every application is different. The plating source can help you choose.

Alex

 

[stonerabroad]

chrome plating is a very hard brittle coating. although wear resistant, it too will flake off over time with repeated impacts. since the coating is so hard, it develops microcracks which propagate through rather quickly.

although pretty, it requires copper or nickel prestrikes to get a somewhat durable coating.

electroless nickel is an amorphous coating, that is rather tough. additional hardness can be achieved with heat treatment. i've been getting all my parts EN plated because of the simplicity of the process and attractiveness of the final part. coating thickness is easily controlled as well, and coating is done at near room temperature.