-- The Home Page of the Finishing Industry

on this site
current topics

60,000 Q&A topics -- Education, Aloha, & Fun

topic 8094

Tin Plating Finish Problem on Aluminium Castings - Fungus Formation


I have a finishing problem of tin plating on machined aluminium castings (shape & size : cylindrical - ~6 cm. dia. x 6 cm. height). The surface finish of the aluminium castings after machining is about 3 to 4 microns Ra. The method of plating followed is detailed below :

1. The machined castings are washed in a solution of soap oil to remove excess oil & burrs and degreased in a trichloroethylene bath and wiped clean with a soft cloth before plating.

2. The tin plating bath is prepared with sodium stannate powder diluted with water. The pH of the above sodium stannate solution as measured with Litmus paper is found to be between 10 and 11.

3. The cleansed aluminum castings are dipped in the sodium stannate bath for about 2 minutes, then immediately dipped in a cold water bath and again dipped in a hot water bath for 3 to 5 seconds each. The castings are wiped clean with soft cloth again.

The problem is : Fungus like formation (black spots) on the surface on the tin plated aluminium after about 24 hours when kept in normal factory atmosphere.
Environmental Conditions : Temp. : 30 to 36 °C Humidity : 75 to 80 %
Factory with aluminium foundry and machine shop inside the same building.

Any procedural flaws in the tin plating method or environment may please be pointed out. Can any additives or catalysts improve the tin plating longevity?

B C Pai
- Chennai, TN, India


Read your problem, Fungus type marks are observed due to two main components left unattended. 1st Plating time is less and 2nd while in around Chennai because of Higher TDS in water, you need water rinse followed by DM Water Rinse Followed by Hot DM Water Rinse.

Further nowadays a newer concept of Tin Plating is Acidic Tin Plating has come into figure stands much better in Aesthetic Look as well corrosion resistance.

Arun Kumar Ralhan
- Patiala, Punjab, India

this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

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 Compliance

©1995-2020, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.