dsanders,

There are so many particulars as to which is the best coating for a given corrosive situation, generalizations can be very misleading. That said however, if you are talking about normal atmospheric corrosion, without any special conditions, I would agree with you in principal. The reasons being, stainless steel forms a "self healing" chromium oxide on its surface that protects it from corrosion when it is in it's passive state. (assuming oxygen is present in the vicinity, which it would be in normal atmospheric corrosion) This oxide film protects it against many environments very well. Galvanizing of carbon steel is second because it isn't self healing, and will wear out eventually, but it is better than paint, because if a holliday occurs, zinc, in most evironments, protects the exposed steel sacrificially through cothodic protection. As far as paint, I am no expert, but I would think powder coating usually produces less holidays than other types of application and could therefore provide better protection all else being equal, which it seldom is. However, zinc rich paint can do better than powder coating in some circumstances, as it also provides cothodic protection like galvanizing does. Something else to consider is weathering steel, such as "Cor-ten" (a trade name), which when exposed to the atmosphere, forms a rust coating that does not flake off like normal carbon steel, and therefore stops corroding. The main hiccup bing if a rusted appearance is acceptable, and if the environment is correct for this application. (Although the rusted appearance is in vouge in some parts of the country) This type of steel is popular for bridges as it can reduce initial costs over stainless, and maintainence costs over paint/galvazinig.


If you are referring to corrosion protection other than general atmosphercic, please post more details, and perhaps someone can give more specific ideas.


I hope this is more of a help than a confusion.

G Roberts

I have to agree with GRoberts that generalizations can be very misleading. In some environments, S/Steel will fail quicker than C/Steel. In addition, not all S/Steels are equal, or all paint coatings etc.

If you can give us a specific environment, we could probably give you better info.

Regards
Niekie Jooste