Small Rust Spots

[spindel]

I'm in the process of welding in new front and rear fender panels on my '72 240Z. There are also a number of very small rust spots around the rear wheel arches, and along the front of the hood. They range in size from about 1/8 to 1/4 inch in diameter. Is it possible to simply clean them as best I can, perhaps apply phosphoric acid (like Ortho) and spot weld some new metal on top, and have a repair that won't bubble through in a few years?

The alternative is to cut each or them out and weld in a small patch.

Anyone have any experience along these lines?

Many thanks.

Bob

[26th-Z]

Bob,

Spots are usually bigger once you get in to them, but if they are less than 1/2" diameter, you can drill them out an exact diameter and weld a flush "punch" back in. Look for a slug punch tool from some place like Eastwood that makes a metal slug in a specific diameter from sheet metal. There are a range of sizes available and it beats trying to make a patch.

Drill a hole that is much bigger than the rust bubble to get the rust around the edges of the bubble. The slug fits flush and it is a true metal patch.

Watch out with acids. Make sure you clean the area to get all the acid off.

[spindel]

Great idea! Many thanks. (And thanks for the caution about acids.)

[26th-Z]

There's a lot of info on the net about using acids for rust removal. Some of the more concentrated acids such as Naval Jelly (35% phosphoric acid) can do some damage if not cleaned off properly. Acid in that high concentration will eat the metal. Something like OPSHO (less that 12% phosphoric acid) is considered a rust encapsulator because it is so weak.