[Bazz4CQJ]

In the OP, the comment was that there is a ‘rust patina’, which I take to mean a very light degree of rusting. That being so, I too think that I’d start and see if it can be removed by a wire brush or even iron wool and perhaps follow that by oxalic acid (probably just wiping). Hydrochloric acid seems like the nuclear option. I wouldn’t go within 20ft of any restoration project with any chemical containing chloride ions, which includes numerous domestic cleaning products. Phosphoric acid will create a layer of iron phosphate on the steel, which is potentially a problem at any grounding points.

The link to zinc chromate paint in post#7 actually takes you to a page selling zinc phosphate. All chromates are now regarded with deep suspicion from a H&S standpoint (especially in aerosol form), hardly anyone still supplies the consumer market and zinc phosphate is a very good paint.

B