external corrosion / pitting on aluminium cylinders - how bad?

[Still Kicking]

Main problem with aluminum tanks that have been exposed to saltwater/humidity for long periods is galvanic corrosion around the sealing land at the neck. Check for bubbles under the valve. If you have bubbles it may or may not seal with some cleaning (scotch pad) and a new oring.

As others said, the tanks in the photos look fine to me.

 

[blue sky]

A couple of years ago, I came across a Luxfer’s Scuba Cylinder Visual Inspection Guide

The red text on the first page is my notes.

 

[SlugLife]

A couple of years ago, I came across a Luxfer’s Scuba Cylinder Visual Inspection Guide

The red text on the first page is my notes.

Giving this a quick skim, it covers a lot of the same material as the Visual Inspection class I just took, and appears well written. This may not exactly the same as getting Visual Inspection training (It doesn't cover things like ISO cylinders, steel cylinders, or other manufacturers), but would be a good guide for anyone who wants to do preliminary inspections of their own cylinders, or perhaps be a more informed buyer of used tanks.