Bare Aluminium Corrosion

[Babylon]

My tiller has a black-painted aluminium bracket screwed underneath it, to which the autohelm is connected when in use. The old black paint was flaking off the bracket, so I have now removed it to the bare aluminium, which has polished up nicely.

My options are either to prime and paint it again, or to leave it bare polished alluminium, which looks quite smart. What will happen if I just leave it bare - will it 'tarnish' or corrode?

 

[oldsaltoz]

<<<will it 'tarnish' or corrode?>>>

Yes, it will tarnish, turning to a flat finish then grey then whiye and pitted.

If you like the polished look keep it covered with Vaseline or varnish.

 

[VicS]

If you have polished it nicely getting it anodised might be an attractive option. Thre is an anodising works in Seagull Lane, Emsworth who will do small items.

Success my well depend on the alloy but as far as I know pure aluminium will anodise well.

If you repaint it a suitable primer for aluminium is vital.

 

[Babylon]

[ QUOTE ]
If you repaint it a suitable primer for aluminium is vital.

[/ QUOTE ] Thanks VicS (and oldsaltoz). (Chemistry was always my weak point - I fled my chemistry 'O' Level moments before the invigilator said 'open your papers'... for which I was eventually rewarded by acquiring inlaws who were both research chemists!)

From what you're saying, I assume I need special aluminium primer rather than ordinary metal primer?

 

[VicS]

Yes ideally just one coat of a two pack etch primer. International do one but in a 500ml pack! Maybe you'll have to settle for something from the DIY store. There's a Hammerite "special metals primer" (water based!) but no idea how god or bad it is. Very convenient but otherwise not a fan of Hammerite paints.

Don't fancy the anodising idea then?

 

[oldsaltoz]

Have a look at getting it powder coated, very nie finish and more durable than ordinary paint.

Avagoodweekend......

 

[Superflid]

I used Hammerite "special metals" primer on an outboard leg, it's still doing a good job after 2 years but the Hammerite top coat peeled off after 6 months!

 

[matelot]

I would disagree with the above posters. Ever since the ally on motorbikes was painted there has been a problem of paint peeling and the ally pittin. In contrast, bare polished ally as you see on HD bikes can be kept much more presentable but it will take a little work to polish every so often.

If you have doubts look at your boat pots and pans. they will likely be bare unpolished ally

 

[alexrunic]

polishing and anodising would be a good option. painting is fine as long as you use an etch primer and good quality top coat.

 

[Nigel_Ward]

I agree with matelot!

If you leave the bracket without paint it may be OK. If it corrodes you can paint it later.

My boat has an aluminium head which attaches the tiller to the rudder stock. It is 20 years old, unpainted and looks like new.

Aluminium is a fickle material as there are so many grades. A lot of aluminium commercial boats are left unpainted (just roughened surface) which in many cases has proved to be better than painting.