On Mon, 26 Mar 2007 17:56:36 GMT, "Gordon Wedman"
wrote:



A friend has gone thru this with his stainless. People at his workplace
that know about his sort of thing told him he needed to passivate the welds.
They gave him some solution to paint on the welds. I believe this is
hydrofluoric acid, perhaps a mixture with other acids. Requires very
carefull application. It took away the surface shine. Don't recall the
final result but I can ask him.


Thanks for this Gordon,
At the moment the offending articles are sheathed by masking tape as I
am halfway through spray painting the hull.

I would very much appreciate you asking your friend if it is not too
much trouble. The more information about this, the better.

When it was welded, it, like all other Stainless welds was brushed
with that nitric acid gel solution that then is washed off with water,
and which removes the discolouration from the tig/mig/arc welding
process. Is this the same thing? I can't recall getting anything
"passivated".

Thanks and cheers
Peter

On Mon, 26 Mar 2007 17:50:22 +1000, Peter Hendra
wrote:

On Mon, 26 Mar 2007 17:56:36 GMT, "Gordon Wedman"
wrote:



A friend has gone thru this with his stainless. People at his workplace
that know about his sort of thing told him he needed to passivate the welds.
They gave him some solution to paint on the welds. I believe this is
hydrofluoric acid, perhaps a mixture with other acids. Requires very
carefull application. It took away the surface shine. Don't recall the
final result but I can ask him.


Thanks for this Gordon,
At the moment the offending articles are sheathed by masking tape as I
am halfway through spray painting the hull.

I would very much appreciate you asking your friend if it is not too
much trouble. The more information about this, the better.

When it was welded, it, like all other Stainless welds was brushed
with that nitric acid gel solution that then is washed off with water,
and which removes the discolouration from the tig/mig/arc welding
process. Is this the same thing? I can't recall getting anything
"passivated".

Thanks and cheers
Peter

The acid treatment was "passivating".

My experience is that unless the stainless is polished to a mirror
bright finish you will get staining. All the bits have to be polished;
Assuming that it is a bolt on fitting the bolts and washers that are
exposed to sea water need to be polished.

I've been making things out of stainless and putting them on boats for
quite a number of years and I have found that if the part has all the
welds ground smooth (so the welding ripples don't show), no pin holes
or voids in the weld and then polished bright I seldom get staining.
If I don't do this I always get staining.

A couple of years ago I built a new stitch and glue dinghy. Welded up
a couple of plates with a lifting eye; dosed them with a 20% acid bath
until all the discoloration was cleaned off; gave them a lick with a
sanding disk on a high speed grinder; mounted them and gave them two
coats of epoxy primer and two coats of two part poly urethane
(spelling?). Got "rust" stains. Should have polished them.

By the way, I get my stainless polished at the local chrome shop,
Cheaper then the "stainless shop".

I also take care to bed everything with either 3M or Sikaflex. Much
better then household "silicone" sealant.

I've been reading some of your other posts -- do you reckon that your
paint job is cheaper, or more expensive then it wold be in Malaysia?



Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

On Tue, 27 Mar 2007 16:53:07 +0700, Bruce
wrote:


I've been reading some of your other posts -- do you reckon that your
paint job is cheaper, or more expensive then it wold be in Malaysia?



Bruce in Bangkok
(brucepaigeatgmaildotcom)

Hi Bruce,
Thanks for the info.

It looks as if I shall have to take my stern ladder off and polish it
as you say. Yes, I always use Sikaflex.

As to the relative cost of the paint job, haven't really done the
sums. I have to get it done so I just spend what I need to. The paint
is relatively the same - I am using Ameron - made by the people who
own the yard. In Malaysia I used Jotan antifouling which I bought in a
20 litre drum from Singapore and had ferried up to Langkawi by a
series of patrol boats (free of course). I can't recall the price but
it seems rather expensive here. I am considering ABC3 but have to test
it on a metre square patch as to whether it will adhere to the
existing Jotan (I should post an enquiry regarding this).

The other difference and increase in cost for me is that in Malaysia I
had free use of the 30 ton travel lift at our Langkawi Marine Customs
base as well as the large new shed to paint in. Here I am paying yard
fees and small extras such as daily rental for planks and scaffolding.
There is an extra daily charge for living on the boat whilst in the
yard. I plan to take my mast down and renew the rigging and do a
number of other things. Rental is also charged on the mast whilst it
is on the ground.

In Langkawi there is an excellent stainless workshop as well as
experienced electrical and mechanical engineers - all very cheap.
Here, prices for labour and services are much dearer, partly due to
the large American and other customers who are happy to pay the
somewhat cheaper cost than in the US.

One price I do know that you should be able to trealte to was the cost
of having two hatches re-teaked - US$75 per square foot.

Also, here I have no car so have to purchase most groceries at the
local minimarket which has marina pricing unless I want to take half a
day off to buy only that which I can carry on a maxi taxi. In Langkawi
I could have my meals at the Customs Base.

Another difference, not factored in any financial calculations, is
that here there are many like minded souls who are able to give advice
regarding things boating. In Malaysia, by nature of my job and the
close knit family style of Customs and because my wife and son were
with me, I mainly socialised with locals and met few yachtees.
Actually, many of the later disliked me before they had met me as many
were annoyed that I had access to Customs bases and facilities
throughout the country. One even officially approached the commander
of the Penang base and asked why he was not able to tie up there,
leave his dinghy there in security and get water etc. as I did. No
amount of telling them that I worked for Customs seemed to satisfy
them. Also, I was regarded with suspicion (sometimes in quite a
hostile manner) by some as a lot of yachtees sailed up from places
like the marina at Port Dixon to load their boats with duty free
cigarettes and alcohol which they sold or shared with their
neighbours. They expected me to do something about it and curb their
activities but frankly I and we had other priorities and never worried
much about yachts. We knew of it but let it pass as Customs is kept
busy by contraband smugglers, the heroin traffic from Thailand, and
human trafficking. One specially built GRP boat with three new Mercury
200HP outboards bringing 2.5 tons of cigarettes from Indonesia avoids
$615,000 Ringit of duty (US$178,000). I have seen two of these
apprehended in one night at the Port Klang base.

Besides, many of these yachtees I had nothing in common with anyway
and they had spent years drinking and socialising in the one place as
a way of life. They won't leave and there are those that finance
themselves by selling off vital equipment from their boats. There were
others, however, who were great company such as Bob and Ely and their
delightful two little boys who, at aged 4 and 5 could climb to the
spreaders - no mast steps, just pull themselves up a halyard - and sit
and eat their bag of potato chips. Bob, a retired military man, a rock
conservative fundamentalist Christian from the Mid-West, who at age
75 is on his third marriage, will help anyone with their radio or
electronics. He now is moored at a Marine base in Penang most of the
time - a wonderful man.

Hey, I apologise - I got carried away.

Yes, thinking about it - it is cheaper in Malaysia but commercial
haulout is much dearer there.

cheers
Peter

Bruce wrote:

The acid treatment was "passivating".

My experience is that unless the stainless is polished to a mirror
bright finish you will get staining. All the bits have to be polished;
Assuming that it is a bolt on fitting the bolts and washers that are
exposed to sea water need to be polished.

I've been making things out of stainless and putting them on boats for
quite a number of years and I have found that if the part has all the
welds ground smooth (so the welding ripples don't show), no pin holes
or voids in the weld and then polished bright I seldom get staining.
If I don't do this I always get staining.

snip...
Bruce in Bangkok
(brucepaigeatgmaildotcom)


Hi Bruce,

I've just recently started building stainless
parts for my two sailboats. I'm using 316 SS and
316L SS exclusively and passivating with Citrisurf
which is a strong citric acid. It can also be
used for electropolishing, and I intend to try
using it for that in the future.

Google "Citrisurf". It is supposed to be better
and more environmentally friendly than nitric acid
paste. Several of the welders that post to
sci.engr.joining.welding have used it with good
results. I've only started using it about six
months ago, so the stuff I've built has not been
out in the salt spray long enough to tell how good
the passivation was.

Don W.

On Tue, 27 Mar 2007 17:35:18 GMT, Don W
wrote:



Bruce wrote:

The acid treatment was "passivating".

My experience is that unless the stainless is polished to a mirror
bright finish you will get staining. All the bits have to be polished;
Assuming that it is a bolt on fitting the bolts and washers that are
exposed to sea water need to be polished.

I've been making things out of stainless and putting them on boats for
quite a number of years and I have found that if the part has all the
welds ground smooth (so the welding ripples don't show), no pin holes
or voids in the weld and then polished bright I seldom get staining.
If I don't do this I always get staining.

snip...
Bruce in Bangkok
(brucepaigeatgmaildotcom)


Hi Bruce,

I've just recently started building stainless
parts for my two sailboats. I'm using 316 SS and
316L SS exclusively and passivating with Citrisurf
which is a strong citric acid. It can also be
used for electropolishing, and I intend to try
using it for that in the future.

Google "Citrisurf". It is supposed to be better
and more environmentally friendly than nitric acid
paste. Several of the welders that post to
sci.engr.joining.welding have used it with good
results. I've only started using it about six
months ago, so the stuff I've built has not been
out in the salt spray long enough to tell how good
the passivation was.

Don W.

Don,


I've tried things ranging from purpose made passivating stuff to
vinegar. At the moment I am using a tile cleaner sold, here in
Thailand in every supermarket, that is 20% hydrochloric acid.

One comment I probably should make is that all the passivation
chemicals work by dissolving (eating) some material from the surface
of the piece being worked on. Of course this is how it works, removing
all the oxides and other rubbish from the just welded surfaces. BUT,
it also etches the nice shiny surface of the expensive piece of
stainless you just welded.

My experience is that if you don't polish the etched surface back to a
mirror finish you still get staining.

In another message I mentioned some dinghy lifting brackets I made
that stained. They had been left in acid overnight and were perfectly
clean but with a matt finish when I installed them -- thought the matt
finish would hold the paint better -- wrong.



















Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

On Wed, 28 Mar 2007 07:44:50 +0700, Bruce
wrote:


I've tried things ranging from purpose made passivating stuff to
vinegar. At the moment I am using a tile cleaner sold, here in
Thailand in every supermarket, that is 20% hydrochloric acid.

One comment I probably should make is that all the passivation
chemicals work by dissolving (eating) some material from the surface
of the piece being worked on. Of course this is how it works, removing
all the oxides and other rubbish from the just welded surfaces. BUT,
it also etches the nice shiny surface of the expensive piece of
stainless you just welded.

My experience is that if you don't polish the etched surface back to a
mirror finish you still get staining.

In another message I mentioned some dinghy lifting brackets I made
that stained. They had been left in acid overnight and were perfectly
clean but with a matt finish when I installed them -- thought the matt
finish would hold the paint better -- wrong.

Bruce in Bangkok
(brucepaigeatgmaildotcom)

Thanks again Bruce,
There is just so much to learn
Peter