-- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

on this site
current topics

topic 0108

Poor coverage in barrel zinc plating

A discussion started in 1995.
Add your Q. or A. to restore it to the "Current Topics" discussions.


1). parts are app 1/2" long, hollow tube, dia. = major app .280, minor app.160 1/2 and 1/2 of the tube. material looks to be bronze, parts have little to no coverage on tip of minor dia. only, id and balance look well plated. parts do nest, but fall apart easily, plate is zinc with clear plate looks to be for luster only. advice on coverage problem?

2). parts are a knurled ferrule, 1/2 dia. x 3/4 long, material bronze id is threaded. poor id plate, knurl plate is fair at best 1/16th area on ends not knurled no coverage, looks almost like masked (but not). ends of piece, no coverage at all, finish zinc with clear

note: parts almost feel slippery where not coated, acid zinc line

3). zinc die cast, 1 1/2" long, 1" dia., one end protrusion, 3/8 dia. x 1/2 long plate exhibits blistering and poor coverage on protrusion very end luster looks good, blue white coverage of part looks good, even in deep recesses on id finish - zinc with clear these are all done on the same line, are we exhibiting a line problem?, or a parts problem. these are the only reported problem parts for this zinc bbl line are these all symptoms of the same problem?, customer says solution and anodes are up to snuff but maybe he's not looking in the right place?

Ron Landrette
plating equipment supplier - Bristol, Connecticut


#1 - From the phrasing of the question, I think your customer suspects what the problem is, and he may be right. Sounds like the small I.D. is inserting itself into the larger I.D. during tumbling. If so, there is no easy answer except that a different style barrel, perhaps with breaker bars, may help.
#2 - The part may be leaded brass, with the pretreatment cycle attacking the zinc and leaving passive lead on the surface? Leaded brass is tricky; you may want to have samples plated by a supplier's lab.
#3 - Is this zinc die-cast part polished? The compound may not come off as easy as other soils.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.