Purchon/Cantele discuss corns in their book: The Complete Aromatherapy and Essential Oils Handbook for Everyday Wellness.
Calendula infused oil
They suggest that after bathing, use a pumice stone to remove dead skin from the corn. Using a cotton ball, apply calendula-infused oil to the area. Cover with a bandage or non-stick dressing. Repeat daily until all traces of the dead skin have been removed.
Foot Soak: If the corn is too painful for using the pumice stone, you may want to try a foot soak. In a basin large enough to fit the feet, combine 6 drops Birch essential oil and 1/2 cup Epsom salts. Add warm water to fill the basin about halfway. Agitate to dissolve the salts and dispese the essential oil. Soak feet for about 10 minutes (or as long as desired), then dry. Then follow the suggestion above and apply the calendula oil. Cover feet with thick socks. "Shoes are almost invariably the cause of corns - find the culprits and get rid of them!"

Purchon/Cantele share this tip:
"Hard, thick corns can be difficult to remove. Aspirin can help! The salicylic acid in Aspirin can soften the corn, making it easier to scrub away the dead skin. Using the back of a spoon, crush 5 Aspirin tablets into a fine powder and transfer to a small non-reactive bowl. Add 1/2 tsp (2.5mL) lemon juice and 1/2 tsp 2.5mL) distilled or filtered water; stir to form a paste. Apply the paste to the corn and wrap the foot with plastic wrap. Cover the area with a hot dry towel and leave it on for 10 minutes. Rinse the foot under warm running water, then gently scrub with a pumice stone. Follow with a few dabs of calendula-infused oil and cover with a soft bandage."

1. I had ordered your Golden Salve a while back and recently my husband was asking if I knew of anything I had that might help him with a painful corn. For some reason I gave him my little jar or Golden Salve and told him I thought he ought to try it until I could do some research about it. I forgot to look into, and he faithfully applied the salve day and night feeling like it was helping. Eventually the corn disappeared. His sister had the same problem, so he offered her some salve, and she had the same results. This is great stuff.

2. I put some Clove oil on a corn under my toe morning and night, and it less than 3 months it completely disappeared. That was two years ago - it's really gone.

3. I have had a very painful corn between a couple of toes that overlap and rub each other wrong. I decided to try Citrus Blessing on it morning and night. The corn hasn't gone away, but it is without pain now, and I feel like it will go away given time.

4. My corns were on the bottoms of my feet, and it hurt so much to walk. It felt like I was walking on nickel-size pebbles. I tried putting some oils on and then sanding the corns, but that made my feet hurt for days. That just didn't work well for me. I felt like giving up, but then I decided to try Citrus Blessing, which seemed to bring the most relief. With consistently applying this morning and evening (I use a 10ml roll-on applicator), the corns are literally melting away! They are not completely gone, but it's only been about 3 weeks since I became consistent with this. I figure that the corn didn't get there overnight, so I can't expect them to disappear overnight either. I can at least walk normally again.

Reference
Purchon, Nerys; Cantele, Lora, Complete Aromatherapy and Essential Oils Handbook for Everyday Wellness, 2014, pages 229-230.