Introduction
Experimental
Preparation of the metallic substrates
Pretreatments
Coating morphology and composition characterization
Impedance measurements
Salt spray testing
Results and discussion
Coating morphology
Impedance measurements
Days | ||||
---|---|---|---|---|
0 | 1 | 4 | 7 | |
AA2024-T3 Alodine 1200 | ||||
R
s (Ω cm2) | 23.0 | 9.4 | 8.4 | 3.6 |
R
ct (Ω cm2) | 1.32 × 105
| 6.3 × 104
| 5.1 × 104
| 1.3 × 104
|
C
dl (µF cm−2) | 8.89 | 3.90 | 4.92 | 11.81 |
AA2024-T81 Alodine 1200 | ||||
R
s (Ω cm2) | 22.9 | 16.8 | 5.4 | 5.4 |
R
ct (Ω cm2) | 2.0 × 105
| 7.6 × 104
| 6.3 × 104
| 6.0 × 104
|
C
dl (µF cm−2) | 5.78 | 6.61 | 24.68 | 6.48 |
AA2024-T3 PreCoat A32 | ||||
R
s (Ω cm2) | 7.6 | 11.3 | 7.4 | 3.7 |
R
ct (Ω cm2) | 4.8 × 105
| 1.3 × 105
| 6.9 × 104
| 6.9 × 104
|
C
dl (µF cm−2) | 0.37 | 1.09 | 1.99 | 4.14 |
AA2024-T81 PreCoat A32 | ||||
R
s (Ω cm2) | 12.8 | 13.3 | 8.1 | 6.6 |
R
ct (Ω cm2) | 5.6 × 105
| 5.0 × 105
| 4.5 × 105
| 3.9 × 105
|
C
dl (µF cm−2) | 0.02 | 0.07 | 0.02 | 0.02 |
Salt spray testing
Aluminum alloy | Alodine 1200 | PreCoat A32 |
---|---|---|
AA2024-T3 | No/little evidence of corrosion | Few density corrosion spots/pits |
AA2024-T81 | No/little evidence of corrosion | Few-medium density corrosion spots/pits |