Classic/Antique Car Repair: Cleaning engine and under-carraige parts, acid dip, removing rust from metal

Question
QUESTION: Hello Jorge. I seek your advise on cleaning auto parts of oil, carbon, sludge and rust. I have read in a magazine on how very dirty parts can be cleaned with an acid bath or acid dip. What acid is recommended?


ANSWER: Hello Yahaya. i would clean greasy and oily parts in a strong degreaser. for parts that have hardened baked on carbon deposits like exhaust valves or very rusty parts than a acid bath will do the job. Both phosphoric acid and sulfuric acid will work. please be careful.

---------- FOLLOW-UP ----------

QUESTION: Can't find phosphoric acid in my area, or is it called by another name? Can I use hydrochloric acid, and at what strength (diluted)? Will the acid not affect the good part?

Answer
if you are removing rust from metal than you you use it full strength. if you are using it on alloys then dilute it 10 to 1 10 parts acid one part water.hydrochloric acid is stronger than phosphoric sulfuric is also about the same as hydrochloric as far as the reaction to rust. the acid will not affect good metal as quickly as it will dissolve rust you need to monitor the progress. be careful