Fluff on my Calipers

Hoping someone can shed some light on why the callipers in images below are coming back (twice – different shops) with that white ‘florescence’.

I’m guessing its some type of contaminant, but as they were prepped prior to dipping I’m wondering is there a ‘standard’ procedure for preparing brake callipers before dipping...blasting/dipping/rinsing etc etc..?

I have a recollection of reading something about wire brushing the calliper bodies before dipping but can’t remember where I saw that.

I checked out Eric Sheas restoration blog http://www.ferrarichat.com/forum/showthread.php?t=304911 via the ‘Dino 246 restoration blog’ but didn’t see any detail about the plating.

Incidentally all the other items I’ve had replated (by one of the shops) have returned perfect – whether gold or silver plate.
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Looks like these are zinc or zinc-nickel plus chromate plated?
Not sure if anyone there does actual cad plating now. If they just did zinc it might explain the fast corrosion.
I think the porosity of the cast iron accelerates the corrosion.
Bead blasting or wire wheeling to close the pores is possibly the answer. Check with an expert.
I found Adelaide Brake Service in Norwood were the most helpful, if they are still there.

I had quality issues with plating being done in Adelaide 15-25 years ago, high end restoration shops could not get chrome done properly anywhere, very frustrating.

 

Paul,

Zinc plating cast iron is always challenging because of the material's porosity, and moreso when the material you are dealing with is old and has absorbed contaminants. You almost always get some white spots on cast iron but admittedly I've never seen anything nearly as bad as what you show in your pics. Some suggestions:

Make sure your plater is using a chloride (aka acid zinc) plating process instead of an alkaline plating. The two processes are simply different ways of depositing the zinc on the part, however when dealing with cast iron, acid zinc is really your only choice to get a proper plate. Your plater should know this.

Make sure that all previous plating is removed. This might seem obvious but sometimes you will have a part that looks perfectly clean but still has a layer of plate on it. In particular if your part was at some time nickel plated (no reason it should have been, but thought I would mention it) then the new plating simply will not stick until all of the nickel has been removed. Cleaning is best done via shot blasting or via chemical means by your plater.

Hope this helps.

Best Regards,
Paul

 

Thanks Guys,

I think I'll oversee a chem dip, then shot blast then wire wheel to smooth over.

Paul.