Originally Posted by
Karl Robbers
Yep, understand that funds are tight, but a poor man pays twice they say.
Using your 100X50X4 channel as an example, that sounds awfully like Duragal Channel, which is not in fact Galvanised at all. It is merely a zinc enriched coating and nowhere near the thickness or durability of a proper hot dip galvanised finish. 100X50 channel is probably too small in section to build a good trailer with to be honest.
Regarding galvanising, the way our local galvaniser works out pricing is as follows. Weight of component (in your case trailer) X 1.07 X 1.73 + GST. So for a 300Kg trailer frame the cost would be 300 X 1.07 X 1.73 $555.33 + GST = $610.86
Remember to take into account the width of the bath when designing and building anything that will be galvanised. In the case of our plant, the bath width is 950mm.
$600 dollars may seem a lot, but it doesn't take all that long to rack up a hefty bill when buying industrial quality paint, prepping the surface etc.
Another option may be to use RHS and FULLY seal all joints, then drill a hole and fill all members with a decent bit of oil, then weld the hole closed, before painting the outside with good quality paint.