Significato e scopo
5.1 La corrosione esterna dei metalli verniciati è influenzata da molti fattori, tra cui: atmosfera corrosiva, piovere, condensando la rugiada, luce ultravioletta, wet/dry cycle and temperature cycle. These factors often have synergistic effects on each other. This practice is intended to provide a more realistic simulation of the interaction of these factors than conventional testing with continuous exposure to a set of static corrosion conditions.

5.2 The results obtained from this exercise can be used to compare the relative durability of materials subjected to a particular test cycle.

5.3 No exposure test can be specified as a complete simulation of actual conditions of use in outdoor environments. Only when a rank correlation has been established for the particular material being tested can the results obtained from the exposure performed according to this practice be considered representative of the actual outdoor exposure. The relative durability of materials in actual outdoor service can vary considerably from location to location due to differences in UV radiation, wet time, temperatura, contaminanti, e altri fattori. Così, even if results from specific artificial test conditions are found to be useful for comparing the relative durability of materials exposed to specific external environments, it cannot be assumed that they can be used to determine the relative durability in different environments.

5.4 Although very tempting, it is not recommended to calculate an “acceleration factor” that relates x hours of laboratory exposure to y months of external exposure. Different materials and different formulations of the same material may have significantly different acceleration coefficients. The acceleration factor also varies according to changes in degradation rates in laboratory tests and actual outdoor exposures.

5.5 This practice is suitable for comparing the relative performance of materials tested simultaneously in the same exposure device. Since there may be differences between the same type of exposure equipment, it is not recommended to compare the amount of degradation in different equipment exposed to the same duration of material at different times or running the same test conditions. This practice should not be used to establish “passare/fallire” approvals for materials after a specific exposure period unless performance is compared relative to control materials exposed at the same time or variability in testing is rigorously quantified so that statistically significant pass/fail judgments can be made.

5.6 This practice has been found to be useful for air-dried industrial maintenance coatings on steel 3,4,5,6,7 and zinc-rich primers, but its applicability in high UV stability coating systems, such as automotive applications, has not been evaluated.

ASTM D 5894-2021 “Esposizione ciclica alla nebbia salina/ai raggi UV dei metalli verniciati (o Esposizione a camere di nebbia salina/essiccazione e camere UV/condensatore)”

Ambito di applicazione
1.1 The practice covers the fundamentals and operational practices of cyclic corrosion/UV exposure of paint on metal, with alternate exposure in two different cabinets: a cyclic salt spray/drying cabinet and a fluorescent UV/condensing cabinet.

1.2 This practice is limited to methods and procedures for obtaining, measuring and controlling exposure conditions. It does not specify the preparation of the specimens or the evaluation of the results.

1.3 I valori espressi in unità SI devono essere considerati valori standard. Altre unità di misura non sono incluse in questo standard.

1.4 Questo standard non è destinato ad affrontare tutti i problemi di sicurezza, se presente, legati al suo utilizzo. È responsabilità dell'utente di questo standard stabilire la sicurezza adeguata, pratiche sanitarie e ambientali e per determinare l'applicabilità delle restrizioni normative prima dell'uso.

1.5 La presente norma internazionale è stata sviluppata in conformità con i principi di standardizzazione riconosciuti a livello internazionale stabiliti nella Decisione sui principi per lo sviluppo di norme internazionali, Linee guida e raccomandazioni emesse dal Comitato sugli ostacoli tecnici al commercio dell'Organizzazione mondiale del commercio.