Stainless Steel & Galvanic Corrosion
After three years of the stainless steel production being on the decline due to stock cycles and the overall global crisis concerning our economy there is now an exciting turn as stainless steel melting activities increased by 24.9%.
The growth in stainless steel melting probably occurred because there is now a strong end us for stainless steel such as its use in construction. Refilling the internal supply chain in the stainless steel mills, which alone counted for half a million tons and then the glimmer of hope that the economy is now in the early stages of recovery.
This is exciting news for the stainless steel industry however, with a stong end use demand like construction it would seem that consideration of the compatibility of different mixed material assemblies is often something that gets overlooked when in the design stage, fabrication and installation.
This is something which is important and needs to be considered, stainless steel a “noble” material is used regularly in direct contact with other more common metallic materials. Although stainless steel can withstand corrosion the problem lies with the material that it is within direct contact with.
They form a galvanic partnership; it is this partnership which raises concerns for the other material due to stainless steel adopting a corrosion resistant property. Due to the galvanic partnership which is formed accelerated corrosion of the less noble material will occur. This accelerated corrosion rate can be quicker than the normal rate of this metal if it hadn’t been partnered with stainless steel.
Corrosion related damage which can occur in this way often can lead to premature replacement of this item. What is more, the use of various fixings such as rivets, screws and fastenings when placed in direct contact with stainless steel may actually corrode because they are less noble and if there is running water then this can lead to streaks down the stainless steel which prove to be unsightly and stand out on the shiny stainless steel sheet.
For galvanic corrosion to occur then there has to be different corrosion potentials of the metals within a given system, a conductive connection between the two metals and an electrically conductive humidity film – an electrolyte connecting both metals.