HyLife TM HVAC Line Corrosion testing. Precision Tubing Technology Centre, 2012

Transcription

1 Precision Tubing Technology Centre, 2012

2 Background: There is an increasing interest in the use of aluminium tubes for connecting lines for residential HVACR applications Connecting lines are often covered with a thermal insulating foam Extensive testing have been executed to investigate risk of corrosion underneath the foam and in the coupling/flare joint fitting area potentially caused by condensation on the tube, particularly in hot climates Test setup: Sample configuration: Flare joint with brass fitting, heat shrink sleeve on one side of the brass fitting, no protection on the other (Test 2) Line-set with insulating foam (Test 1) Tube material: Hylife TM HVAC Line alloy, 9,53 x 1 mm (*). Cu tube used as reference material *HyLife TM HVAC Line samples prepared for test are courtesy of Ebrille, Italy

3 Corrosion test conditions: Test 1: Accelerated salt spray corrosion test, ASTM B117* -> Line-set with thermal insulation Test 2: Accelerated salt spray corrosion test, ASTM G85-94-A3** -> Coupling area, flare joint with brass fitting * Deionised water solution with 5 wt% NaCl. ph neutral, Cabinet temperature: 35 C, Samples placed longitudinally in the chamber, Altubes with foam with defects and Cu-tubes with foam with defects introduced, Tap water at approx 10 C were running continuously through the tubes during testing, Test duration: 42 Days, continuous fog of the 5 wt% salt solution at a rate of 12 ml/hr, Samples taken out at selected intervals and characterised ** Synthetic sea water adjusted to ph by acetic acid, Cabinet temperature: 49 C, Two-hour cycling: 30 min spray followed by 90 min soak >98% RH, Tubes locked at each end, test duration 1000 hours

4 Artificial defect area in insulating foam Test 1: Line-set with thermal insulation Macro characterization after 42 days of exposure Slight corrosion formed underneath the edge of thermal insulation foam No salt ingress from the tube ends as they were covered with plastic fittings Salt ingress from the defect area and minor corrosion Metallographic examination (42 days) Minor pits up to max µm in the area without foam Similar setup with copper tube had max. 50 µm No corrosion under the foam Outside the thermal insulation 100 µm Under the thermal Insulation 100 µm

5 Test 2: Flare joint with brass fitting Macro characterisation, photos before and after testing Without heat-shrink sleeve (Not recommended) - Direct galvanic coupling between the brass nut and the Al tube thus rapid corrosion subsequent failure With heat-shrink sleeve (Recommended) - No significant corrosion taking place Metallographic examination (40 Days) Without heat-shrink sleeve (Not recommended) With sleeve - Significant corrosion Leakage in the aluminium just outside the brass fitting in the non insulated region With heat-shrink sleeve (Recommended) - No or very little corrosion in the insulated region 0 Days 40 Days No sleeve x With heat-shrink sleeve No sleeve

6 Conclusion Coupling area: No corrosion under a well applied heat-shrink sleeve Line area: No or very limited corrosion under the thermal insulation foam. Very limited corrosion in areas were the thermal insulation was missing Recommendation Coupling area: A properly applied heat-shrink sleeve must be covering the HyLife TM HVAC connecting line and onto the brass coupling. Line area: The Thermal insulation foam should cover the complete connecting line from coupling to coupling not exposing the tube to the environment