Summary for carbon black attacking aluminum Discussion
Carbon black in black inks attacking aluminum is the question raised by Brian Hill, who asked whether carbon black in inks can attack aluminum when the ink is applied to hot stamping foil. Robert H. Probert answered that carbon black itself is not the issue, but the solution’s pH is critical: anything about one pH unit away from neutral 7.0 can attack aluminum, especially when heat is involved. The thread does not present a conflicting view; instead, it points to pH control as the key factor to check before blaming the pigment. In practical terms, the discussion suggests that if aluminum is being attacked, the ink formulation’s acidity or alkalinity is more likely responsible than the carbon black pigment alone.
Q. Is there any evidence to support carbon black in inks can attack aluminum. The application is ink applied to hot stamping foil.
Brian Hill
– Lexington, North Carolina, USA
October 3, 2012
A. Carbon Black per se, NO, but what is the pH of the solution. Any pH ± 1 away from 7.0 will attack aluminum, particularly with heat.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
First of three simultaneous responses — October 4, 2012
A. I do not know about carbon, but I do know that a common pencil marking on Al in a coastal area will slowly eat through it.
James Watts
– Navarre, Florida
Second of three simultaneous responses — October 4, 2012
A. I would check the MSDS of the particular ink you are using. If there are certain solvents in your ink, that could be a cause of corrosion.
Aluminum in itself, is very susceptible to corrosion, hence the need for coatings.
Without seeing a picture of your situation, I’m also wondering if the “corrosion” you are noting is the ink actually preventing that natural oxidation of aluminum that will occur around the inked areas.
Marc Green
anodizer – Boise, Idaho
Third of three simultaneous responses — October 5, 2012