Rust in Peace

I think I may have hit on the problems I'm having with my spot welding not creating an electrical circuit in certain areas.

After wire brushing with a rotary wheel, any remaining areas of rust are coated in Jenolite, which is essentially phosphoric acid. This chemical reaction creates iron phosphate, which is inert and forms a protective layer that is less prone to rust - the reason I use it.

According to Google Bard, which is my go-to reference (except for political questions, where it becomes a bit reticent and ChatGPT is more forthcoming), iron phosphate exhibits a type of electrical conductivity called polaronic conduction. This means that while it does conduct electricity to some extent, it's not very efficient. 

Iron phosphate (FePO₄) is generally considered an insulator in its pure form. However, impurities and specific conditions can influence its conductivity. In particular, iron phosphate can exhibit polaronic conduction, where electrons move through the material by "hopping" between different iron ions that exist in different oxidation states (Fe²⁺ and Fe³⁺). This type of conduction is less efficient than the free flow of electrons in metals, making iron phosphate a poor conductor compared to metals. 

The conductivity of iron phosphate can vary depending on factors like:

• Crystal structure: Different forms (polymorphs) of iron phosphate can have different electrical properties. 
• Doping: Adding impurities (dopants) can modify the electronic structure and influence conductivity. 
• Temperature: Conductivity often increases with temperature in materials that exhibit polaronic conduction. 

Therefore, while iron phosphate isn't a great conductor in its pure form, it's not entirely non-conductive, and specific modifications can influence its electrical properties. Spot welding in the cold can't help.

Or, am I overthinking this?

Finally got the last bit of lower front wings off the bonnet on Friday, and what a faff that was. 

The issue was having to retain the rear stiffener bracket around which the rear of the new panel is crimped when fitted. The first side took me about an hour, whereas the other side was much quicker, as I'd learned from taking off the first side. The repair panel is now clear to be inserted.  

I received the Argon/CO2 gas and the Clico fasteners on Saturday but, as expected, I need all manner of connectors, which are on order. The Clico fasteners will be particularly invaluable, as the repair panel needs some force to be applied to it to get the correct curve from fore to aft. Ordinary welding clamps wouldn't really do a good job of lining up the panel, whereas Clicos will be perfect.

In the meantime I will continue to remove all the layers of paint, take the whole thing back to bare metal and fix any slight dents. It's a hideous job - the white layer of paint under the yellow has been trowelled on in a thick layer and the red primer sticks like nuclear glue.

I'm starting to suspect, from the thickness of the layer of white paint, that it's actually a thick layer pf primer that was applied to the original green paint before covering it in yellow top coat.

It's the single, largest panel and has to be stripped topside and underside. A mammoth task which will take 3 or 4 days to do properly. I also uncovered some quite large dents at the front edge of the bonnet from shunts, which will require hammering out before refilling and smoothing with filler.