Reducing the Pitting Corrosion on an Evaporator Tube using the Quantum-Transported Life-Stress Model and Sample Size

To resolve the problems such as fatigue or pitting corrosion on a low-cost evaporator tubing in a household refrigerator, the tube material was changed from copper (Cu) to Aluminum (1070 Al) by applying parametric accelerated life testing (ALT). This systematic strategy included the following: (1) ALT plan used on BX lifetime that will be X percent of the accumulated failure, (2) corrosion effect modeling, (3) ALTs with revision, and (4) estimation whether the design attained the objective BX lifetime. A quantum-transported life-stress model and a sample size producing reliability quantitative (RQ) statements were proposed. A case study investigation for this methodology was employed to enhance the lifetime of a household refrigerator whose evaporator tubing was failing in the field due to aqueous pitting or crevice corrosion. In the first ALT, for RQ statements, this failure was reproduced by ALT equipment and the refrigerator tubing that were placed in a 3.5% saline solution for the accelerated condition. The pitted tubing was determined to be nearly identical to those returned from the marketplace refrigerators. Using a scanning electron microscope (SEM) with Energy Dispersive X-ray (EDX) showed that the trouble with the evaporator tubing came from water condensation and direct chlorine contact on polyvinyl chloride (PVC) tape with water-soluble adhesives layer. Three action plans were evaluated. First, the tape material was changed from PVC to polyethylene (PE) with a water-soluble adhesive. Second, the contraction tube was enlarged from 50 to 200 mm. Third, polyethylene foam pads between enclosure case and the tubing were inserted. In the 2nd ALT, the refrigerator tubing showed no corrosion. Refrigerator thus achieved the goaled lifetime—B1 life of ten years.