Table I
Absorption Coefficient of Some Steel Samples (% in Weight, 0.45%, C, 0.8% Mn, 0.3% Si) with Different Surface Finishing Conditions (After Ref. 5)
Surface condition | Absorptance |
---|
Polished | 0.11 |
Blasted | 0.34 |
As is | 0.37 |
Blackened | 0.51 |
Phosphate coated | 0.93 |
Table II
Roughness (Expressed in Microns) of the Surface of Some Steel Samples for Different Values of the Bath Temperature, the Concentration of the Ammonium Persulfate, and the Immersion Time
Concentration (g/liter) | 100 | 200 | 300 |
Temperature | 20° C | 40° C | 50°C | 20°C | 40° C | 50°C | 20° C | 40°C | 50°C |
Immersion time (min) | | | | | | | | | |
1 | 0.2 | 0.65 | 1.15 | 0.4 | 1.0 | 1.3 | 0.65 | 1.6 | 1.8 |
3 | 0.4 | 1.0 | 1.65 | 0.7 | 2.0 | 2.2 | 0.8 | 2.45 | 2.55 |
5 | 0.6 | 1.7 | 3.5 | 2.0 | 2.5 | 4.6 | 2.9 | 4.5 | 5.0 |
10 | 1.0 | 3.0 | 4.0 | 3.0 | 3.5 | 4.2 | 3.5 | 5.0 | 5.8 |
Table III
Roughness and Average Slope (see Sec. II), Measured by the Talystep, of Steel Samples as a Function of the Immersion Time in a Solution of 300 g/liter of Ammonium Persulfate in Water at Room Temperature
Sample | | Roughness (μm) | Average slope |
---|
30 min | A | 6.9–7.5 | 0.35–0.30 |
B | 4.6–5.1 | 0.23–0.23 |
20 min | A | 6.2–5.8 | 0.29–0.29 |
B | 5.4–6.6 | 0.27–0.31 |
15 min | A | 5.6–5.3 | 0.32–0.26 |
B | 6.7–5.8 | 0.27–0.26 |
12 min | A | 3.8–4.6 | 0.24–0.28 |
B | 5.1–4.6 | 0.24–0.28 |
10 min | A | 3.7–4.6 | 0.22–0.25 |
B | 5.0–5.5 | 0.27–0.27 |
5 min | A | 1.9–2.2 | 0.14–0.15 |
B | 2.9–1.7 | 0.20–0.11 |
As is | A | 0.10 | 0.01 |
B | 0.11 | 0.01 |
Optically polished | | 0.03 | 0.002 |
Note: For each value of the immersion time we prepared two samples (labeled
A and
B, for each of which we performed two different measurements.
Table IV
Average Roughness and Relative Reflection Coefficient and Some Steel Samples for Different Immersion Times
Sample | Average roughness (μm) | | Reflectivity |
---|
Opt. polished | 0.033 | | 0.76 |
As is | 0.11 | | 0.03 |
5 min | 0.09 |
| <10−3 |
15 min | 5.46 |
20 min | 6.04 |
30 min | 7.23 |
Table V
Main Characteristics of the Devices Used for the PAR Measurement of Absorptance
Laser pump: | argon laser by Coherent model CH-15 |
Dye laser: | Coherent Model 599 (Tunability 0.51–0.65 μm with rhodamine 6G) |
Microphone: | Model 4166 by B&K, sensitivity 50 mV/W, Bandwidth 3 Hz–9 kHz |
Piezoelectric crystal: | PZT-5A by Vernitron |
Photoacoustic cell: | Homemade |
Table VI
Summary of the Results
Surface Treatment | Roughness (microns) | Average slope | Reflection coeff. (R) | Absorptance (A) |
---|
Optically polished | 0.03 | 0.002 | 0.78 | 0.20 |
Commercial | 0.10 | 0.01 | 0.02 | 0.26 |
Etching time (min) | | | | |
5 | 1.6 |
| <10−3 | 0.30 |
7 | 2.2 | 0.36 |
10 | 4.5 | 0.45 |
15 | 5.8 | 0.47 |
20 | 6.0 | 0.54 |
30 | 6.0 | 0.48 |
Note: We report the average surface roughness (in microns), the average slope, the average reflection coefficient, and the average absorptance as a function of the surface condition. The etching time refers to a solution of 300 g of ammonium persulfate per liter of water at room temperature.