The three metals that do most on a boat are stainless steel, brass and aluminum. They are all corrosive. But some last a lot longer than others and this is the only distinction between them. Which is the useful question, which is which is immune and which can be restored once it has departed?
Use of metal on a RIB
Visible and load carrying functions on a typical fiberglass RIB are performed by stainless steel: ladders, railings, handrails, latches and hinges. Brass is found in the smaller fittings including vents and plugs. The hull is aluminum on an aluminum RIB, and on smaller, more affordable boats, aluminum also is used in the bimini frames and roll bars.
Stainless steel is not coated in any way.
Stainless is the most corrosion resistant material on the boat, and without a protective layer to be worn away. Marine stainless is available in a variety of alloys at a variety of cost, and its corrosion resistance follows suit. If a fitting is weeping rust stains at the beginning of its season, it's most likely a lower grade, not a faulty part.
The plating is not a protection to the brass but a cover.
The majority of brass fittings are nickel or chrome plated. The plating is cosmetic and the protection of the underlying brass from oxygen is not. The part that is doing the work is called the plating. When it is worn out, the fitting is complete: The re-plating is an industrial process and not a garage job so in practice, you replace the entire fitting.
The aluminum has to rely on its coating for its protection.
Aluminum does not corrode as well as stainless or brass and therefore cannot be coated. The typical solution is to anodize it, and as with brass plating it can only be buffed back to a shine under industrial conditions. But, as with most company, aluminum also has its picky moments: if it comes into contact with a dissimilar metal, without separating the joint, galvanic corrosion begins at the point of contact. That's the purpose of sacrificial anodes and maintaining a check on them is a good thing to do once a season.
Standing water is the harbinger of harm!
The routine is short. Never let water come in contact with metal, especially salt water. After rinsing it off, both halves are important - fresh water and being wiped dry by a fresh rag.
Look for water retention sites after all other water sources have drained. Screws and bolts. Fittings that are made up of multiple parts. Water resides there and corrosion begins there before it is visible anywhere else. Out on the boat in the rain doesn't help much, either does boarding in a wind high enough to carry spray. A cover will address both of those.
No one of the three metals is self-maintainable for eternity, and only stainless is close. The one thing on this page that works on all three is the cost of a dry cloth after a salt run, which takes 2 minutes. It can be used as part of the RIB Maintenance Routine (in the Maintenance Guide).