Acid dipped frame

without knowing the circumstances of this treatment, it's almost impossible to say with certainty
whether if it will be bad. all i know is that /i/ would not buy it.

properly controlled factory dip processes are fine and do a good job of preps for may different kind
of subsequent finishing. then again, some alloys can be very susceptible to scc, and some of the
cannondale frames i've seen cut open for inspection have lots of nooks & crannies for acid residues
to remain after an amateur dip.

so, bottom line, unless you know chapter & verse on the dip and that it was done by someone that
knows their business, it's just not worth the risk.

Sasha Nackovski said:

Here's a question for you metalurgist/material technology folks out there.

A dude on ebay is selling a Cannondale road frame that he claims he has had "acid dipped" in
preperation for paint. It is an aluminium frame. I would have thought that the Cannondale factory
would have applied some type of zinc primer or coating to both the inner and outer surfaces of
the tubes before applying paint to the bike. Acid dipping would then remove the anti-corrosion
coating from the tubes, increasing the likelyhood that the inner tubes would suffer from
electrolytic corrosion. Would this be a correct assumption? If this were the case then, would it
be a bad idea to purchase this frame, keeping in mind that I can only really paint the outer
surface of the tubes?

The seller also claims that the frame is a Cannondale "Caad 2.8". I have never seen or heard of
this model designation. What gives?

Thanks,

Sasha

Sasha Nackovski said:

A dude on ebay is selling a Cannondale road frame that he claims he has had "acid dipped" in
preperation for paint. It is an aluminium frame. I would have thought that the Cannondale factory
would have applied some type of zinc primer or coating to both the inner and outer surfaces of the
tubes before applying paint to the bike.

What, you mean galvanized aluminum? Of course there is a primer, on the outside only, but we are
talking aluminum. Corrosion is not that much of a problem.

Quoted message said:

Acid dipping would then remove the anti-corrosion coating from the tubes, increasing the
likelyhood that the inner tubes would suffer from electrolytic corrosion.

What are you worried about? Unless you see a lot of saltwater on your rides, you will not get
significant corrosion on an aluminum frame. I had one that was bare, and had not corrosion problems.

Re: the acid. Lord knows what he really used, and what effect that might have had on the frame. I
would not spend a lot, at any rate.

--

David L. Johnson

__o | If all economists were laid end to end, they would not reach a _`\(,_ | conclusion. --
George Bernard Shaw (_)/ (_) |

There is little risk of the frame diminishing in strength but if you have a bare aluminum frame
(acid dipped or otherwise) it will quickly form an innocuous but obnoxious film of aluminum oxide,
which brushes off on clothing and virtually anything else as black stain. If you chose to purchase
the frame you should either have the frame professionally clear coated or anodized and it should be
fine, providing it was fine prior to being stripped.

David L. Johnson said:

Sasha Nackovski said:

A dude on ebay is selling a Cannondale road frame that he claims he has had "acid dipped" in
preperation for paint. It is an aluminium frame. I would have thought that the Cannondale factory
would have applied some type of zinc primer or coating to both the inner and outer surfaces of the
tubes before applying paint to the bike.

What, you mean galvanized aluminum? Of course there is a primer, on the outside only, but we are
talking aluminum. Corrosion is not that much of a problem.

Quoted message said:

Acid dipping would then remove the anti-corrosion coating from the tubes, increasing the
likelyhood that the inner tubes would suffer from electrolytic corrosion.

What are you worried about? Unless you see a lot of saltwater on your rides, you will not get
significant corrosion on an aluminum frame. I had one that was bare, and had not corrosion
problems.

Re: the acid. Lord knows what he really used, and what effect that might have had on the frame. I
would not spend a lot, at any rate.