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Auto body repair & detailing/Use of Phosphoric Acid


Good morning,

I am getting ready to use some phosphoric acid and "Rust Bullet" on various metal panels on my 1967 Ford F100 Pickup.  The phosphoric acid is called "Prep and Etch."

Here is my question: Should I wash off the acid (with water) after 30 minutes or so?  Or should I leave the phosphoric on the metal overnite and then wipe it off with a damp rag?

Thank you for your help.


Hi John!...Although I have never used phosphoric acid myself,(as it is a controversial product for us), it is sometimes used in the Autobody Industry. What I have used in the past, is a product called "Metal Conditioner". The purpose of the metal conditioner, is also to deep clean and etch the metal. The proper procedure for this, is to dilute the conditioner with water in a plastic container, and according to label instructions. Once this is done, it is recommended to be applied to the bare metal with a spray bottle only. Leave it on for only a few minutes, then continue to rinse off the area with clean water, and wipe it dry completely. That being said, it is possible that phosphoric acid is also an ingredient in the metal conditioner. Unfortunately, I have never checked out the label on the Metal Conditioner to find out. I trust it, due to the fact that it is recommended for Autobody metal prep, and I have had great results with it. In all honesty, I would recommend using a Metal Conditioner versus using straight Phosphoric Acid. Metal Conditioner has been proven to be more than effective, and I definitely can't say with a conscience, that using straight phosphoric acid will give you the same results....Hope this helps you out..If you have any other questions, please do not hesitate to ask....Thanks for your question...Dave

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Dave Norgardt


Absolutely anything autobody related... Frame repair, suspension, alignment, panel replacement, panel repair, fiberglass, plastic repair, paint, air bags, etc.....


Over 30 years in related areas. 25 years in HEAVY frame repair, suspension, and alignment procedures. As well as panel replacement and repairs, etc.....

Journeyman Autobody Technician with Red Seal/Interprovincial certification from N.A.I.T. in Edmonton, Alberta, Canada. Top Achiever award second year, also from N.A.I.T. Also have Platinum status from I-Car Canada...Also have Journeyman Partsman Certificate, Lethbridge, Alberta...

Awards and Honors
Second Year Top Achiever from N.A.I.T.Edmonton

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