| Source
Newsletter 2006 issue 3 |
|
 |
Low Quality Steel
| |
 |
| |
Crater caused by steel defect |
Getting at the cause of defects can be a lot like the ever-present “Not me” in the Family Circus cartoon. With a coating defect, painters point to the pretreatment baths, the chemical vendors point to the quality of the steel being painted...
Maybe it is the steel. While China’s growth feeds increased steel demand, U.S. manufacturers more frequently get lower quality steel. Inability to identify the poor quality until parts rust, show zebra striping or break after forming or painting results in defects that waste time and money.
At a recent Chemical Coaters Association educational program, David B. Chalk, Ph.D., of Galaxy Associates, Inc., explained the steel making process to help people better identify and manage defects, and to stand a better chance of getting satisfactory steel from the mill. His tips:
- Specify a steel sulfur-content of less than 0.0085 percent. It will cost a little more, but it’s worth the improved performance and consistency of final products. The phosphorus and silicon content will be reduced in these steels as well.
- Always use a conversion coating to prepare for painting. The coating passivates the surface and minimizes the corrosion problems presented by contaminants.
- Reject and return steel that has a “speckled” corrosion pattern on the surface, shows signs of excess surface carbon, or does not exhibit the required mechanical properties. Often, the cause is high levels of impurities.
|
|
Table of Contents
Other Source Issues
|
