Knowledge base · Technical note
SS201 or SS304 for outdoor storage units?
The material question that decides whether a lock still looks and works the same after two winters. The answer depends on where the unit is, not on the budget alone.
The short answer
SS201 for indoor units and covered corridors. SS304 for exposed outdoor and coastal locations. Both are legitimate choices — the mistake is using one grade everywhere because it was cheapest at the time of the first order.
Why the difference matters
Stainless steel resists corrosion because of a passive oxide layer. In SS304 that layer is more stable in the presence of chlorides — salt air, coastal humidity, road salt — than in SS201. In a covered corridor the difference rarely shows. On an exposed door near the coast it shows as surface staining first, then pitting, then a shackle that no longer moves freely.
How to classify your site
- Indoor / climate controlled — SS201 is normally sufficient.
- Covered corridor, inland — SS201, with plating quality doing most of the work.
- Exposed door, inland — SS304 recommended.
- Coastal or de-icing salt exposure — SS304, and consider the finish specification as carefully as the grade.
Specify the finish, not only the grade
Grade and finish work together. Electroplating and coating quality decide how long the visible surface holds up, and salt-spray testing is how that is verified. Ask for the salt-spray record for the finish you are ordering — for the model you are ordering, not for a different product in the same catalogue.
The cost conversation
SS304 costs more per unit. The honest comparison is total cost over the replacement cycle: an SS201 lock that has to be replaced early costs more than the SS304 lock that did not, once labour and administration are counted. Tell us where the units are and we will recommend per location rather than applying one grade to the whole site.
Confirm it on your own doors
Send a door photo, the cylinder size or the mounting dimensions. We confirm fit with a physical sample before you commit to a quantity.
What readers ask next
Once the site is classified, the questions get specific.
Is SS304 enough for a coastal site?
SS304 is the grade we recommend for exposed and coastal locations, and the finish matters as much as the grade. Send the distance to the water and whether the doors are covered and the specification is confirmed.
Can we order SS201 and SS304 in one batch?
Yes. The two grades can travel together, separated by area so the crew fits the right one to the right door. Send the count for each area.
What is the price difference between the two grades?
SS304 costs more per unit because of the material. Both are quoted for your quantities so the difference can be weighed against the replacement cycle, and the recommendation is made per location rather than one grade site-wide.