Breathe easy! No maddening pop-up, sticky, or floating ads on this site :-)

Home /
Search 🔍
the Site
pub Where the world gathers for
plating, anodizing, & finishing Q&As since 1989


Defect in shiny anodized product

none is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

for Shops, Specifiers & Engineers

"Aluminum How-To" -- Chromating, Anodizing, Hardcoating by Robert Probert (2005)
avail from

"The Metallurgy of Anodizing Aluminum" by Jude Mary Runge (2018)
avail from eBay, Abe Books, or Amazon

"The Surface Treatment & Finishing of Aluminium and Its Alloys" by Wernick, Pinner & Sheasby (1959 - 2001)
avail from eBay, Abe Books, or Amazon

"Anodic Oxidation of Aluminum and Its Alloys" by V. F. Henley (1982)
avail from eBay, Abe Books, or Amazon

"Surface Treatment and Finishing of Aluminum" by Robert King (1988)
avail from eBay, Abe Books, or Amazon

The Technology of Anodizing Aluminum by Brace (1979)
from Abe Books or Amazon

"The Anodic Oxidation of Aluminum" by A. Jenny (1940)
avail from Abe Books or Amazon

Anodizing and Coloring of Aluminum Alloys by S. Kawai (2002, VERY RARELY avail)
from eBay, Abe Books, or Amazon

(as an Amazon Associate & eBay Partner, earns from qualifying purchases)

Q. I have a problem in shiny anodized product -- appears on surface after cleaning and polishing.

61433-1a   61433-1b  

Cold stamped aluminum, then mechanically polished, and then transferred to the anodizing line
HNO3 (50-60 °C)
polishing (85% H3PO4, 15% HNO3, 110°C)
anodizing (15 min, 20 °C, 190 g/l H2SO4)

Mai Thi Ngoc ÁNh
staff - nam dinh, Vietnam
May 4, 2022

A. What is the alloy? Heat treated? Suspect Chloride contamination from the water, or iron drag into the anodizing from the deox.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

Q. I have a similar problem on the bright anodized product. The top of the parts has a defect that does not go away when rubbing. The defect appears more in the upper rows of the rack and always on the top of the pieces. Sometimes it also appears on the sides of the rack. It appears before anodizing.

61433-2c   61433-2a   61433-2d   61433-2b  

Our process is:
We use alloy 5657
bright dip (H3PO4, HNO3 and H2SO4)
deox (diiron trisulphate, sulphuric acid, nitric acid)
anodizing (195 g/L, 20 °C, 17 min)

S Llinares
- Spain
November 16, 2023

A. S Llinares

It looks like the Brite Dip solution is drying on the part(s) prior to rinsing. Consider a faster transfer to the rinse, or add a spray rinse over the Brite Dip tank. If you are operating the BD at >100 °C, water added via rinsing should boil off in a timely manner.

Willie Alexander
- Green Mountain Falls, Colorado
November 19, 2023

thumbs up sign Insightful answer, Willie. I bet you're right.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey

Q. Thank you. I will try adding a spray rinse over the Bright Dip tank.
I have read that you can increase the wetting additive in the Bright Dip, do you know what wetting additive to use?

S Llinares [returning]
- Spain
November 20, 2023

A. S Llinares:
We used an R5 Bright Dip many years ago. No additives required other than seeding with a little copper. I am unaware of any wetter you could use. Sorry.

Willie Alexander
- Green Mountain Falls, Colorado
November 21, 2023

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully 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 might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2023, Pine Beach, New Jersey, USA