"Brush Plating"

[jbknudsen]

Greetings to all!!!

I am working on a project requiring a 3" bore to be refurbished in a localized area (approx 2" long encompassing the bore. The customer is wanting to "brush plate" the bore and then re-polish the surface. I am not familure with with process. I have found a few web-sites but I am still left with some questions.

1) How thick is a typical application?
2) Does a thicker or thinner application adversely affect the properties of the application?
3) Is this process typically used as a tempory fix or is it considered permanent?
4) How does the process stand up to cyclic operations @3000 psig with the piston seals contacting the refurbished surface?
5) Is the plating prone to flaking off?
6) If a scratch is developed, will the scratch propagate within the plating surface and cause flaking.

I know that some of the questions will are specific for my application. However, I am trying to find out if anyone else has experience with this type of electroplating. If so, is this generally acceptable as an alternative to welding and re-finishing the bore.

Thanks for any info.

Jay

 

[swall]

Brush plating is generally considered a "touch up" process rather than an engineering coating. With the brushing, you just don't have enough exposure time to build any significant film thickness.

 

[arto]

Cogsdill has a knurling-burnishing method of restoring oversize bores:

http://www.cogsdill.com/pdf files/usbur_kb.pdf

OK as long as you don't need a totally smooth surface [ends up with flats & grooves - good for holding glue/oil or press fit.]

 

[kenvlach]

Brush plating, also known as selective electrofinishing, can meet MIL & NADCAP & NASA specs and be used for permanent work. Three big suppliers of equipment & chemical solutions & services (with informative websites, too) are
Brooktronics

http://www.brooktronics.com/

Liquid Development Co.

http://www.ldcbrushplate.com/homepage.htm

SIFCO

http://www.brushplating.com/main.asp?zone=1&detail=0

 

[yates]

Brush plating simply means electrolytic plating where the electrolyte is not a bath of liquid, but rather liquid applied with a brush. This technique is normally only used for touching up unplated areas (typically elctrode contact points from a prior electrolytic plating operation in a bath) Results are far superior with bath plating using a suitable masking medium to prevent plating of unwanted areas. The post does not mention what type of plating, this of course could be cadmium, zinc, nickel, silver, tin... so the questions on wear resistance etc. can only be answered once this is known. I assume the call-up is for chrome plating, as this is some kind of bore.

 

[unclesyd]

It has been my experience that trying to restore a small section of such a bore is not worth the effort especially on the higher pressure cylinders. The biggest problem is no matter what the partial repair process you will always have a transition area where the problem will manifest itself again but much more quickly.

The better methods that I've used is skin the whole cylinder and plate the entire bore or if real bad bore the entire cylinder oversize, plate with iron and then Hard Chrome Plate or undercut the bore and reweld the entire length and remachine.