spud15
No that appears to concur with what I've done
- "when using acid etch .. the metal should be ... washed .. then etch primer applied"
No, its not very well worded but you need to read it again. In that section acid etch means the etch primer. Acid wash is termed metal conditioning in these notes. Washing off acid treatment with water then drying is part of the metal conditioning process, and is an etch for epoxy primer.
To clarify "The second is an acid etch (primer) which should
not be applied over metal conditioner (phosphoric acid treatment) as they are both etching agents and this may cause delaminating.....never etch an etch...." They drummed never etch an etch into us every night.
and at the top of the notes in bold
Metal conditioning should not be done if using an acid etch primer....
The bit you have quoted means when using acid etch (primer) the metal should be sanded, washed
with wax and grease remover etc.....not acid treated and washed with water.
Another common misconception is that etch primer can be top coated.
So what they taught us is that there are two ways to prime a car ready for top coat.
1. Metal condition (acid wash) and epoxy primer...the best, fastest and newest way.
2. Sand, degrease, etch prime, prime...the old way and more work since 2 applications of primer.
It sounds to me that you might be metal conditioning with phosphoric acid based products and then etch priming which could cause problems, or it could just be that the terminology you are using to describe what he is doing is confusing. But if you are using an acid based etch primer after treating with ranex etc then I think it would be wise to call the paint manufacturer.
Since blasting is a mechanical etch its probably ok to use etch primer since no chemical reaction possible, but not necessary unless there is a time delay before painting. My blaster just uses 2 pack epoxy but applies it straight way.
While I'm at it another thing they drummed into us is never bog over bare metal. At a granular level, air is trapped and the heat of the bog going off causes condensation which starts the rusting process under the bog, which causes it to eventually crack - we've all seen it in these old cars. Its still common practise in smash repair to bog over bare metal because cars are not expected to last, and repairs have to be fast and cheap, but for classic car restos meant to last they say the only way to go is to only ever apply bog over epoxy primer. It bonds really well and will never rust.
Like I said not claiming to be an expert just passing on what I was taught by the guys that teach the smash repair industry and also spray show cars.