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Trial Number 0

Client Number 116

Project Number 1

Trial Purpose:

To evaluate cleaning efficiency of new system which uses no chemistries.

Date Run:

11/10/1999

Experiment Procedure:

Two sets of OSEE readings were made. The first was to determine a baseline level for the supplied substrate and the second set was to evaluate cleaned parts. Optically Stimulated Electron Emission or PEE, Photo Electron Emission is based on the principle that metals and certain surfaces emit electrons upon illumination with ultraviolet (UV) light. These electrons can be collected, measured as current, converted to a voltage and digitally displayed. A surface contaminant will either enhance or attenuate this signal, depending on it own photoemissive nature. While OSEE will not identify a contaminant, it is a good comparative tool to determine the degree of contamination. This method is best suited for thin films (oils, etc.) and not particulate matter (dust, for example).

The set of coupons were initially weighed and then cleaned using Dawn Dishwashing Soap and a nylon brush. After rinsing and drying, the coupons were weighed again. This process was to ensure the samples were completely cleaned. The baseline coupons were then analyzed using the OSEE instrument. Five readings were taken for each coupon. The coupons were then coated with the insoluble oil using a swab. OSEE readings were taken again in the same five areas of the coupons. Any differences in the clean and dirty readings were recorded and would be used in the evaluation of the client cleaned parts. OSEE readings were measured for the clean coupons from the client. Values were compared to both the baseline values.

SUBSTRATE MATERIAL: Hot Rolled Steel ASTM A-56
CONTAMINANTS: Oil-Chem Ecol Insoluble Cutting Oil
CONTAMINATING PROCESS USED: Parts received clean. Baseline samples coated using swab.

Trial Results:

Initial observations made during the baseline determination yielded a decreased OSEE reading when the coupons were coated with the oil. Table 1 lists the readings made for each coupon and the average values.

Table 1. OSEE READINGS Baseline Determination

Coupon # Left Right Bottom Top Middle Average Difference
19C 352 424 379 359 297 362.2  
19D 314 305 299 276 224 283.6 78.6
20C 337 374 380 353 295 347.8  
20D 290 330 312 307 243 296.4 51.4
21C 314 301 334 304 285 307.6  
21D 295 265 302 291 265 283.6 24
22C 386 333 329 395 296 347.8  
22D 340 281 282 332 258 298.6 49.2
23C 406 444 420 348 328 389.2  
23D 332 299 332 275 255 298.6 90.6
24C 329 310 349 338 296 324.4  
24D 258 284 211 277 256 257.2 67.2
25C 329 316 346 334 294 323.8  
25D 317 293 309 290 256 293 30.8
26C 333 375 429 380 325 368.4  
26D 314 314 284 267 258 287.4 81
27C 396 376 481 395 367 403  
27D 324 333 308 302 263 306 97
28C 413 337 398 346 355 369.8  
28D 283 280 300 292 260 283 86.8
29C 378 346 343 393 328 357.6  
29D 297 304 296 264 258 283.8 73.8
30C 344 364 387 366 337 359.6  
30D 285 306 325 306 264 297.2 62.4
31C 336 347 348 376 314 344.2  
31D 320 286 288 331 254 295.8 48.4
32C 306 280 301 283 272 288.4  
32D 243 260 290 277 261 266.2 22.2
33C 339 323 356 331 319 333.6  
33D 283 283 314 288 268 287.2 46.4
34C 369 385 363 462 391 394  
34D 287 337 326 288 274 302.4 91.6
35C 335 272 328 328 289 310.4  
35D 266 230 262 275 253 257.2 53.2
36C 310 339 357 397 301 340.8  
36D 302 296 280 258 252 277.6 63.2
Average Clean 348.5  
Average Dirty 286.4  
Average Difference 62.1

It was assumed that the OSEE readings for the client cleaned coupons would be in the middle 300 range based on the baseline determination. The actual readings for these cleaned coupons were much lower than the baseline values. The readings were even lower than the dirty OSEE readings. Table 2 lists the readings made and the averages for each coupon.

Table 2. Client Cleaned Coupons

Coupon # Left Right Bottom Top Middle Average
1 223 182 226 214 224 213.8
2 210 198 202 216 215 208.2
3 225 204 187 192 215 204.6
4 228 224 223 225 224 224.8
5 200 228 176 215 220 207.8
6 207 207 221 208 218 212.2
7 217 193 220 223 220 214.6
8 223 208 229 216 228 220.8
37 227 222 222 224 228 224.6
10 212 200 213 207 208 208
11 224 203 220 220 207 214.8
12 216 203 181 217 206 204.6
13 204 219 212 202 206 208.6
14 211 206 204 216 212 209.8
15 203 213 224 203 203 209.2
16 211 210 224 203 205 210.6
17 209 218 211 213 213 212.8
18 194 209 219 202 227 210.2
Average OSEE Readings 212.2

One coupon from the client cleaned coupons was used in a check of the effects of the oil on the Hot Rolled steel coupons. OSEE readings were made in four locations on the numbered side of the coupon. The coupon was then coated with oil as in the baseline evaluation. Four more readings were made and then the oil was wiped off the parts and a final set of OSEE readings were taken. As seen in Table 3, the oil made the readings go up on the client supplied coupons.

Table 3. Reevaluation of Oil Effects on Substrate

  L R T M Average
Clean 178 183 214 192 191.8
Dirty 223 260 261 259 250.8
Re-clean 190 214 168 166 184.5

Success Rating:

A cleanliness study, addressing only various analytical techniques.

Conclusion:

Using the non-client cleaned coupons as a baseline for the evaluation of cleaning effectiveness of the system proved inadequate. Two problems were identified with the method. The first was the change in clean OSEE readings observed for the client cleaned coupons as compared to the non-client cleaned coupons were dissimilar. Secondly, the oil had different effects on OSEE readings for the two coupon types. The oil made readings go down for the non-client cleaned coupons and up for the client cleaned samples.

In order to accurately measure cleaning efficiency of the new system, a consistent analysis method needs to be identified. Gravimetric analysis would be ideal only if the balance is accurate enough to observe the small changes in weight due to the addition of oil. A balance that can read 0.0001 grams has proven effective at the Surface Cleaning Lab.

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