303 & 304 Stainless compatibility
303 & 304 Stainless compatibility
(OP)
Is there any reaction that takes place when 303 and 304 series stainless steel come in contact with each other? I know these are pretty similar in composition. Is there any increased corrosion of the material if for example a 303 series threaded rod were threaded into a 304 series threaded hole?





RE: 303 & 304 Stainless compatibility
Nick
RE: 303 & 304 Stainless compatibility
NickE is correct in that 303 contains 0.15 wt% C vs. 0.08 wt% C in 304. However, 303 typically has an extra 1 wt% Cr to compensate (average 19 % Cr vs. av. 18% Cr in 304).
Some producers add 0.6% Mo (optional) to 303 to improve resistance to pitting.
All things considered, and especially if you passivate to remove surface Mn, there should not be a galvanic problem between 303 and 304.
The worst problems I have seen with threaded connections involving 303, 304, 304L, 316 and 316L and combinations thereof involve galling (cold welding). This can occur under thread loadings as small as 1000 psi. Advise using an anti-galling thread lubricant – many have been recommended in this forum. For more information on galling between various SS combinations (self and dissimilar), request Carpenter Technologies' SS Manual. Galling information is in the chapter on Fabrication. http://www.cartech.com/cartech/WRLProdDisplayServlet/?product=0501&leftn=sao_products&lefto=empty&lefti=sao_pl0
Hope this helps,
Ken
RE: 303 & 304 Stainless compatibility
Chad
RE: 303 & 304 Stainless compatibility
The simple answer is no. They are basically the same alloy with the exception of sulfur. The 303 can also be very low carbon. I have seen some at a .015 carbin level.
One other thing to realize, 303 will crack, especially in small diameters due to the sulfide stringers whereas 304 will not crack.