PSI - Issue 46

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Seong-woo Woo et al. / Procedia Structural Integrity 46 (2023) 169–174 Seong-woo Woo et al. / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 4. A crevice corrosion due to low PH, high Cl- concentration, depassivation and IR drop

As seen in Fig.4, the root causes of the pitted evaporated tubes in a cooling enclose came from the cotton adhesive tape with high concentrated chloride. These design defects could cause the refrigerator to be instantly pitted when subjected to repeated corrosive loads. It may be abridged as: (1) passive film breakdown by Cl + attack; (2) fast metal dissolution: Al  Al +3 + 3e - ; (3) electro-migration of Cl - into pit; (4) acidification by hydrolysis reaction: Al +3 + 3H 2 O  Al(OH) 3  + 3H + ; (5) big cathode: outer surface, small anode: pit; (6) the enormous voltage drop (Ohm’s Law V = I R). To prevent the pitted evaporative tube from the repeated corrosive stresses over the product’s lifetime, the cooling enclosure was altered as follows: (1) enlarging the distance of the contraction tube, C1, from 50.0 mm to 200.0 mm; (2) exchanging the cotton adhesive tape, C2, to the generic transparent tape (Fig. 5).

(a) (b) Fig. 5. Altered cooling enclosure: (a) former design, (b) brand new design

In the 2nd ALT, there were no design issues of the cooling enclosure in a refrigerator until the test was performed to 6,000 cycles. We therefore inferred that the altered designs acquired from the first ALT were accomplishing a desired result. Table 1 outlines the consequences of parametric ALT. With the adjusted designs, the last cooling enclosure system samples are reassured to attain their lifetime target of B1 life 10 years.