Strange problem ,all of a sudden?

[MrPontiac]

Yellow zinc plating 4 nuts, they have concave washers on them and the nuts spin, ok, ive had great luck so far plating lingage but these darn things are giving me fits. First off the area around the o.d. of the washers will not plate, ive tryed differant currant settings but if i go to high then the coating all over comes off to small currant zinc plating is not staying on, so my questionis this, should i acid edge these nuts first for a try?? Surface prep is as follows, i glassbeaded them ,then wire wheeled them to a shine but the area around the outside dia. of the washers are not being plated and it flakes off?? any idea or anyone else had this probelm?? 2.0 amps on my rectifier for 20 min.

[lcaswell]

What was on these parts before you glassbeaded them?

It's always best to degrease before blasting, to avoid blasting oils into the metal.

What's the total surface area of your parts you are plating?

[MrPontiac]

Black Oxide on the nuts, there only 1/4 in nuts with a 3/8 washer on them, glassbeaded them

[lcaswell]

You need to remove the black oxide first with a dip in 20% muriatic acid:80% water.

Did you work out the surface area of the parts? There's a formula in the back of the manual for working out area of fasteners. If you didn't, and are just guessing, you're going to get very inconsistent results.