yes
reduce metal porosity? no. you can clean with acetone, or hit with phos-acid like PPG 579 or similar, then acetone to clean some shit up. Do a burn off in the area before striking and arc.
take some pictures and send them to my email or something. that sheetmetal is not that thick and I still think you’re pulling contaminates in from the backside of the pool/HAZ from too much heat.