**4. Conclusions**

Developing coating systems for 3D printed polymer structures that protect the structural surface against aggressive environmental conditions is critical for the long-term durability of the structures. In this study, multi-material 3D printing was used to deposit an ASA coating on the surface of ABS structures to protect the structure against UV radiation, moisture, and heat. The uncoated ABS samples suffered significant degradation in the mechanical properties, particularly in the failure strain and toughness, during environmental aging. However, ASA-coated ABS specimens largely retained their initial mechanical properties throughout the environmental exposure.

**Author Contributions:** Data curation and Investigation, R.W.; Conceptualization and Writing—original draft, A.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to thank Provost Office at Mercer University for the SEED grant and the support of this work.

**Conflicts of Interest:** The authors declare no conflict of interest.
