When is 317 SS Worth the Extra Cost Over 316 SS?

For most strongly corrosive applications, grade 316 should be more than enough to resist frequent exposure.

However, 317 does achieve better resistance to some specific corrosives than 304 or 316. As noted by an ATI Metals publication, in a boiling test solution of 1% hydrochloric acid, the corrosion rate of 317 SS was 54.2 mils/year, while 316 SS corroded at a rate of 226 mils/year. 317 SS also significantly outperforms 316 SS in sulfuric acid and sodium hydroxide tests.

So, if your processes involve the use of very diluted (less than 3-4%) hydrochloric acid, mild concentration (10%) sulfuric acid, or sodium hydroxide (aka caustic soda), then grade 317 stainless steel might be worth the extra cost over 316 or 304 SS.

It’s important to note that hydrochloric acid in any concentration above 5% will quickly erode any austenitic stainless steel alloy with ease.

Also, in the previously-cited chemical corrosion tests, 317 performed worse against some corrosives than 316, such as phosphoric acid (0.72 mils/year vs 0.2 mils/year) and acetic acid (0.48 mils/year vs 0.12 mils/year).

Ultimately, it takes detailed knowledge about your application and processes to make the right choice for your stainless steel basket materials. If you’re wondering what the best material to use for your custom parts washing basket would be, consult an experienced, degreed mechanical engineer.