Welding Tips and Tricks

Hello,
I am in the process of building a aluminum(6061) snowmobile trailer and the welding is almost complete. What I am worried about is the Salt on the roads in the Winter (Minnesota). At my work we Anodize aluminum for corrosion resistance, but this process is not practical for something as big as a trailer. Does anyone know what manufactures do to aluminum items such as trailers and boats to prevent corrosion? Or is aluminum corrosion resistant enough that no additional finish is required to keep rust away? Any feedback is appreciated.

Hey, Tracks,

Welcome!

The aluminum alone needs no protection, though a coat of paint or clearcoat won't hurt. The weak spot is where steel fasteners attach. Anywhere steel (and especially stainless steel) contacts the aluminum, you have the possibility for galvanic corrosion, which road-salt will accelerate (CaCl is even worse than NaCl). I suggest using a bead of Alumalastic where things like steel spring shackle attach to the aluminum frame, and a coating of "No-Oxide A" on the threads (washers, nuts), of any screw or bolt that penetrates the aluminum. Keeping the salt out of these connections is the key to long life.

Steve S

As mentioned above the aluminium itself will form a protective (invisible) oxide layer and will be fine, however any contact with other metals higher up in the galvanic scale (eg. https://en.wikipedia.org/wiki/Galvanic_corrosion ) can and will cause corrosion issues if water and salt are added.

To combat this it's common to use a paste between any joints that mate aluminium and steel to stop the reaction from starting in the first place. Common on aluminium hull boats with stainless steel fastenings on them for instance.

A few examples are Tef-Gel (http://www.tefgel.com/contain.php?param=tefgel_infor) or DuraLac (http://www.intek-uk.com/duralac.htm). If any boat builders are in your area they probably have other similar compounds available.

Another problem area for aluminium is an effect called 'crevice corrosion' where water and aluminium is trapped in an oxygen-depleted atmosphere (eg. condensation under a rubber mat or similar). The oxide layer is then broken down by the water and it sets off a reaction to create aluminium hydroxide and slowly eats into and through the material causing pitting and holes. So make sure any water can drain/evaporate and it will be fine.

BTW.. Even anodizing only helps partially in these areas as basically it's not much more than an 'extra thick' oxide layer.

Bye, Arno.

Thanks for the information fellas!