[pcm81]

Greetings and salutations.
I've been using dilute sulfuric acid or citric acid for rust removal for a few years now being completely sure that products like evaporust are just a certain concentration of phosphoric acid. Recently i stumbled on this video that is trying to create a DIY version of evaporust and it talks about use of EDTA as a chelating agent, rather than acid. Based on comments i gathered that "real" evaporust also uses sulfur based compound as soap and it may or may not use EDTA as chelating agent (older versions of MSDS list EDTA but in newer versions it is a trade secret).
https://www.youtube.com/watch?v=f9kBdJQMPPI
The author of this video uses 2%-5% concentration of EDTA buffered too PH=7 with citric acid and basically some dish soap.
I am going to try my own formulation of this rust remover and would like your thoughts on my ideas as listed below:

I am going to try to play with additives that are intended to sequester iron from EDTA but i would prefer them not to attack metallic iron from the part itself.
The additives i am consideting are:
1. Sodium meta-bi-sulphate
2. oxalic acid (low concentration) also as ph buffer
3. ascorbic acid
4. Zinc
Basically what i am trying to achieve with these additives is to sequester iron from EDTA but not to attack iron directly.

What do you think about these choices and do you have any better recommendations?
The part i am not sure about is the sequestering of iron from EDTA by an additive. It seems to be, this should be a very slow reaction, this way the iron sequester will not have enough time to attack the submerged part, but given a very long time being in the same solution as EDTA it will have the time to free it from the iron it dissolved.

Thanks ahead