Zinc Plating Bath Comparisons

Question:

What are the basic differences between the various types of zinc plating baths? One of our vendors wants to start plating our parts using an acid zinc type bath instead of the alkaline non-cyanide bath used in the past. What differences can I expect? T. T.

Answer:

There are a number of differences between the two types of zinc plating baths you mention. Space does not allow a complete comparison between types but here are a few differences.

Acid Zinc Type	Alkaline Non-Cyanide Type
Bright deposit - Reasonable substitute for bright nickel	Lower brightness compared to acid zinc bath. Parts are usually chromated after plating. Deposit is darker than other zinc deposits.
Excellent leveling ability	Poor leveling ability
Minimal hydrogen embrittlement	Lower efficiencies– More likely to have hydrogen embrittlement problems.
Poorer ductility especially in thicker deposits	Deposits have less ductility than any other zinc deposit.

As you can see the two types of zinc finishes are not completely interchangeable. You as the customer have to decide which properties are of the most importance to you and then sit down and have a discussion with you plating vendor.

You can find additional information on zinc plating by going to www.pfonline.com and searching the database for articles on zinc plating. A book, which is very detailed, is also available: Zinc Plating by Herb Geduld. The book is available from Metal Finishing Publications, 212-366-3100.