There are several factors to consider when deciding if stainless steel is necessary for your intended use. Remember to consider the specific environments, stresses, and locations that the product will endure. 

1. Corrosion resistance: Stainless steel is highly resistant to corrosion and is able to withstand exposure to saltwater and other harsh marine environments. Zinc plated carbon steel, on the other hand, is less resistant to corrosion and may require more maintenance to prevent rusting. Stainless steel must have at least 10.5% of chromium in it, while carbon steel has chromium under 10.5%. If you plan to use a product in a environment prone to rusting, such as on boats, in coastal environments, or in food processing, stainless steel is the superior option.

2. Cost: Stainless steel is generally more expensive than zinc plated carbon steel. This may be a factor to consider if you are working on a budget. Note that the practical costs may be lower when considering the superior durability of stainless steel in many environments. 

3. Strength: Stainless steel is generally stronger and more durable than low carbon steel. But medium or high carbon steel is stronger than stainless steel per square inch. This can be important if the parts will be subjected to high loads or stress. If using stainless steel as a heavy-duty tie-down, make sure to check the working load limit of your product. Grade 50 stainless steel chain has a working load limit range of 660lb-11,000lb depending on the size. Grade 63 stainless steel chain has a working load limit range of 1400lb-9200lb depending on the size. 

4. Aesthetics: Surface finish and how the two metals reflect light are the visual distinctions between carbon steel and stainless steel. Stainless steel has a polished, shiny appearance that many people find appealing. Zinc plated carbon steel has a more matte finish and may not have the same visual appeal as stainless steel. Another systematic approach to distinguish between the two is to look for evidence of oxidation (red rust). Carbon steels have a high carbon content and are prone to rust when exposed to moisture, whereas stainless steels do not. 

Ultimately, the choice between stainless steel and zinc plated carbon steel will depend on your specific needs and preferences. Consider the factors above and weigh the pros and cons of each option to determine the best choice for your boat. Go-Tow.com has range of Stainless Steel Hardware and Products specific to the marine and boating industry.