Trailer corrosion
Q
I have a three-year-old swinging arm boat trailer with wobbly wheels (by design) on aluminium swinging arms. The steel bolts and nuts supporting the arms are heavily rusted and prevent the arms from swinging freely despite oil and grease. I’d like to replace these rusted bolts with stainless steel, but wonder if there’d be a detrimental galvanic reaction between the new stainless steel items and the aluminium arms? And would there be a galvanic reaction if I replaced the steel bolts on the galvanised frame of the trailer? The trailer is always fresh water washed after immersion in salt water. Geoff Aston, Southampton
COLIN BROWN RESPONDS
For a galvanic reaction to take place you need to have two different metals immersed in an electrolyte. Salt water trapped between components could form an electrolyte but rinsing is usually sufficient to prevent galvanic corrosion.
The steel bolts are more likely to have suffered from simple rusting. You should strip off the assembly to allow full cleaning before fitting new bolts. Stainless steel bolts may last longer and as long as you rinse them thoroughly any retained water would not be salty enough to form an electrolyte.
Replace the bolts with new ones of the same specification as the originals: stainless bolts will have different characteristics from the mild steel or high tensile originals. The manufacturer should be able to give you more advice on this.
There should be no problem using steel bolts with the galvanised steel frame, and using galvanised bolts would delay the inevitable onset of rust.