Hard Chrome Plating Training Course
Appendix 3. Reverse Etch Times
Reverse Etch Times
This table presents reverse etch times for various metals that are commonly hard chrome plated.
Reverse times are given for etching outside diameters at a current density of 3.0 APSI for:
- stick anodes at an anode to cathode distance of 6 inches, and
- conforming anodes at an anode to cathode distance of 0.75 inches.
For inside diameters or flat surfaces, subtract 15% from the times shown.
Unless otherwise indicated, the times below are for reverse etching in a standard 33 oz/gal hard chrome bath, with a maximum sulfate concentration of 1 oz/gal and operated at 135°F.
Other settings can be used, but any differences should be taken into account. For example, using a higher current density and/or closer anode to cathode spacing will decrease the time needed for reverse etching.
The optimal reverse etch time for any particular setup and bath may vary considerably from the values below due to many factors including those related to the anodes, bath chemistry and the condition of the part. It is recommended that until an optimal time is established through testing, that the plater check the progress of etching after 50% of the recommended time (desired condition is a grey mat appearance).
|
Metal Type (AISI)
|
Stick Anodes at 6 inch
Distance Reverse Etch Time (minutes: seconds) |
Conforming Anodes at
0.75 inch Distance Reverse Etch Time (minutes: seconds) |
| Standard Steels | ||
| 1005 - 1039 | 5:00 | 2:30 |
| 1040 - 1060 | 3:00 | 1:30 |
| 1064 - 1095 | 1:30 | 0:45 |
| 1108 - 1119 | 5:00 | 2:30 |
| 1132 - 1151 | 3:00 | 1:30 |
| 1211 - 1215 | 5:00 | 2:30 |
| 1330 - 1345 | 2:00 | 1:00 |
| 1513 - 1527 | 5:00 | 2:30 |
| 1536 - 1572 | 2:00 | 1:00 |
| Alloy Steels | ||
| 4012 - 4028 | 3:00 | 1:30 |
| 4037- 4047 | 2:00 | 1:00 |
| 4118 - 4161 | 1:00 | 0:30 |
| 4320 - 4340 | 1:00 | 0:30 |
| 4419 | 3:00 | 1:30 |
| 4615 - 4626 | 2:00 | 1:00 |
| 4718 - 4720 | 2:00 | 1:00 |
| 5132 - 5160 | 1:00 | 0:30 |
| 8720 | 2:00 | 1:00 |
| Stainless Steels* | ||
| 201 - 304 | 1:00 | 0:30 |
| 305 | 1:00 | 0:30 |
| 308 | 1:30 | 0:45 |
| 310 | 0:45 | 0:24 |
| 316 | 1:30 | 0:45 |
| 316L | 2:00 | 1:00 |
| Magnetic Stainless Steels | ||
| 403 - 416 | 1:30 | 0:45 |
| 440 | 0:45 | 0:24 |
| 501 - 502 | 2:00 | 1:00 |
| High Temperature, High Strength Steels | ||
| 601 | 1:00 | 0:30 |
| 602 - 604 | 2:00 | 1:00 |
| 610 - 616 | 1:00 | 0:30 |
| 630 - 650 | 2:00 | 1:00 |
| 651 - 652 | 0:45 | 0:24 |
| Other | ||
| Cast Iron Grey | 0:05 | 0:05 |
| Cast Iron Chilled | 0:30 | 0:15 |
| Cast Iron Malleable | 0:40 | 0:20 |
| Copper | 0:00 | 0:00 |
| Brass | 0:00 to 0:15 | 0:00 to 0:15 |
| Zinc | 0:00 | 0:00 |
* Etch in sulfuric/hydrofluoric acid tank.