Marine Grade 316 Stainless Steel Stainless Steel Eye Nut High quality Stainless Steel nuts also known as a Lifting eye nut made of durable A4 stainless steel. Full details and technical specifications below. What is A4 Stainless Steel? A4 grades of stainless steel are usually reserved for use in highly caustic environments where improved resistance to pitting corrosion is required, i.e Marine and exhausts. Pitting corrosion occurs once the chromium becomes exhausted through self-passivation after caustic attack - the effects as usually local to the exposed areas. The pitting forms as the Iron atoms become exposed to Oxygen and form 'rust'.. How to use: From time to time small parts and components need replacing on a wide range of machines and accessories for the automotive industry.