ISO 9022-4 is an international standard on Optical inspection and methods for salt fog environmental testing of photonic products. It specifies methods for testing the tolerance of opticalin struts and their add-ons (e.g. mechanical, chemical and electronic equipment) under salt fog conditions. The standard aims to evaluate the corrosion performance of products in salt fog environments, especially corrosion on metal surfaces and clogging of moving parts. Tests Exposure tests are performed on samples by simulating salt fog conditions in marine or industrial environments and changes in their performance are recorded. This standard applies to quality control and Reliability assessment of Optical inspection and photonics instruments, helping manufacturers optimize product design and improve corrosion resistance performance.