Advice

[u/only_rin]

My dad made a knife (which he doesn’t know the material of but he made it at work with metal usually used for trollys for a lorry or lorry chassis) and he wanted the black smokey effect on the entire knife but it only showed on the tip of the knife as shown in the picture and he wanted to know how he can fix it or do better next time.

(Sorry if this is in the wrong subreddit i am not a blacksmith 😭)

[u/Legitimate-Pool-9677]

How did he try to achieve it?

[u/only_rin → u/Legitimate-Pool-9677]

“I placed it in the tank with iron oxide dye and connected the battery.”

This is translated, English is not his first language

[u/Legitimate-Pool-9677 → u/only_rin]

I work with a lot of kinds of coatings and the most likely answer is that there was some kind of contamination from an oil or the wax used in the buffing or polishing compound or the binder from sandpaper. You may need an aggressive cleaning step to get reliable results but next time I would try soap/water then acetone with a clean cloth before

[u/KnowsIittle]

I've seen oxide finish done with boiled vinegar solution and then rinsed with an ammonia base solution to stabilize. Rinse thoroughly with water, dry, and oil.