Stainless Steel. What every boat owner should know. OTB 129.
We look at Stainless steel and some of the things you should know if you own a boat.
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Closed Captions (CC):

00:05
stainless steel what every boat owner
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should know
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in this video we'll be explaining why
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all stainless steels are not created
00:14
equal we'll be telling you how stainless
00:17
steel has properties that make it weak
00:20
how it can actually corrode
00:22
and how stainless steel can leave you
00:24
right in the doodoo when it friction
00:26
welds we'll also be looking at the
00:28
welding of stainless steel and what you
00:30
need to do in order to make it last
00:32
we'll also be looking at the build-up of
00:34
stainless steel and what you need to do
00:36
to ensure components are really good
00:39
stainless
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make sure you watch to the end to find
00:42
out what you should be using on your
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boat
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[Applause]
00:47
[Music]
01:02
stainless steel comes in all shapes and
01:05
forms it can be extruded or drawn into
01:07
rods box sections or tubes
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it can be hot forged into bars and rods
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it can be bent
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shaped
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punched drilled and machined into all
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sorts of shapes
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but not all stainless steels are equal
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they're not all the same chemical makeup
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and it's very important in the marine
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industry that you get the right type of
01:31
stainless let's look at some of the
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basic characteristics of stainless steel
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but before we do remember that stainless
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steel is actually an alloy like brass
01:43
and bronze and types of aluminium it's
01:46
made up from different metals
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stainless steels have the following
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characteristics they're corrosion
01:52
resistant they have reasonably high
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tensile strength and are very durable
01:57
they're temperature resistant easily
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formed and fabricated their low
02:01
maintenance attractive impairments
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environmentally friendly well they're
02:06
recyclable phoretic martensetic and
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duplex stainless steels are classified
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as magnetic whereas austenitic is
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classified as non-magnetic well what
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does that mean
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304 is the most common type of stainless
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steel it contains 18 by weight of
02:25
chromium and about 8 by weight of nickel
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and therefore is often referred to as 18
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8. it is used for many applications
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including cutlery kitchen equipment food
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processing equipment automotive and
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aerospace structural components and
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marine fasteners
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but leave it outside in a marine
02:44
environment for just a couple of days
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and you'll see why it's not the right
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type of steel for you
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so what is the right type of stainless
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steel for us to use on a boat
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well generally it's this middle one
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three one six
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now i'm going to insert a caveat to that
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there are actually many types of
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stainless steel and they range in their
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properties and they're all known by
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different names or numbers but generally
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316 is what you want to use on your boat
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and as a general rule 316 is
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non-magnetic or austenitic so why do you
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need to know that well when you go
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looking for your fixings fastenings and
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stainless steel bits and bobs
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take a magnet with you
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stainless steel has some weaknesses too
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and we'll describe all of them in a
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minute
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but they're quite important
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considerations
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the resistant to ferro oxide formation
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commonly called rust or rusting results
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first from the presence of chromium in
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the alloy specifically from the
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propensity of the exposed chromium atoms
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to form an invisible
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adherent chromium-rich oxide film that
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displayed the further characteristics of
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being able to self-heal
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reform in other words
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in the presence of atmospheric oxygen
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after it's been disturbed i.e scratched
04:09
a variety of modifications to the
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content of stainless steel can improve
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corrosion resistance
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even further and these include
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increasing chromium above the levels of
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eleven percent the addition of eight
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percent or higher amounts of nickel and
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the addition of molybdenum
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which improves the resistance to pitting
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corrosion
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what does that mean in layman's terms
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well generally stainless steel has to be
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clean and polished in order for it to
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form a surface that is impervious to the
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salty sea environment
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to do this it needs to have oxygen
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or air which contains roughly 19 oxygen
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saltwater also contains sufficient
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oxygen to do this provided the water is
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moving that is or can move around it and
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not stagnate
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once the oxygen is used up all the water
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stagnates the oxygen is used up in the
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formation of this impervious barrier
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where there is a lack of oxygen or
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stagnated water the lack of oxygen
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allows the stainless to corrode for
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example in this picture here we call
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this crevice corrosion it has a distinct
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appearance of black pitting of the
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material and may have black liquid
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around it the pitching can be quite deep
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if left unattended it can literally
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corrode right through a bolt fixing or
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flange or fitting
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and note that this is not galvanic
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action
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and can occur in fittings and fixtures
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well above the water line and this is
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one reason that washing your boat down
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every now and then with cold clean fresh
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water will help to preserve the
05:53
stainless steel fittings and fixtures
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and it's another reason why rigging
05:58
chain plates turnbuckles fixtures and
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cotter pins need to be regularly
06:03
inspected regardless of their age
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let's have a look at an example of
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crevice corrosion
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and some of you would have seen the
06:15
video that we did on this volvo water
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muffler before while the outside of this
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device looks lovely and shiny the
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internal starts to rot away from the
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first days used
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many of you will have seen the telltale
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rusty streaks in the bilge if you happen
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to have one of these fitted
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or had to replace it within a certain
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period and that usually is within two to
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three years the causes the worlds on the
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inside are unpolished and untreated and
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crevice corrosion under the clamping
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bands or jubilee clips where they join
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the stainless steel end caps in both
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instances the lack of oxygen causes
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crevice corrosion either in the end cap
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or
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in the worlds and premature failure of
06:58
this component it's not really the right
07:01
material for such a thing to be built
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from
07:04
when we challenged volvo about this they
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said it's a consumable part despite it
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costing 600 euros for you to change at a
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dealer if you want to see the video in
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full i'll put a link in the description
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and at the end of this video
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stainless steel will stretch under load
07:28
there are various tables available that
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can quantify this
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in the various types of steel
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but again in layman's terms as you talk
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the stainless steel bolt or nut
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and loads it will stretch
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as it settles it will not apply the same
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compressive force
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here's an example of that
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your kill bolts will probably be 316
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stainless grade a4 if they're actually
07:57
stainless at all
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they'll be in the region of 24
08:01
millimeters od or diameter
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just under an inch
08:07
the initial torque setting for this size
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of fixing is 603 newton meters or 444.5
08:16
feet pounds
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when dry fitted
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or
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543 newton meters or 400
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feet pounds when lubricated
08:27
if you were to then go back and test the
08:29
torque or check it at a later date the
08:32
stainless steel will have stretched
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applying the same torque again will
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stretch the bolt further
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continue to do this over a period of
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time and the kill bolts will actually
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snap or be severely weakened
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the way around this
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do not re-torque stainless steel bolts
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or nuts
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if you suspect that they were never set
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correctly in the first place then only
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tighten them to sixty percent of their
09:02
original setting from the data sheet or
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replace them entirely with bolts or nuts
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set to the right torque
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you should certainly not be re-talking
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kill bolts made of stainless steel if
09:17
you do not know the history after all
09:20
you wouldn't do it on a car cylinder
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head would you
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and it's the same principle that applies
09:25
here only more so
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while a strong still
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stainless steel has a tendency to work
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harden becoming very hard and brittle
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under repetitive loads
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drilling stainless steel has to be done
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slowly under pressure
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and so that the cutting edge of the tool
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actually cuts
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any rubbing
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or a lack of cutting pressure will
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darken the still and it will work
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hardened to a point that it becomes
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locally harder than the standard high
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speed steel drill bit the trick is
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firstly to drill slowly with a sharp
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drill with a lot of force so that the
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bit cuts clean spirals or swarf from
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both the cutting edges of the drill bit
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use water or a water-based coolant to
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keep the drill bit and the steel cool
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but better still use paraffin or white
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spirit as a coolant and a lubricant if
10:27
you can get hold of them
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use a cobalt bit
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these are extremely hard but they can be
10:33
up to 10 times more expensive
10:36
but these bits are ideal for drilling
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stainless steel but again being harder
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they are somewhat brittle
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when using stainless steel fixings or
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bolts the nuts under load can gall or
10:57
friction world making the nut and bolt
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weld together
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before they are in their final position
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there is just about no cure for this
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other than cutting away the bolt or nut
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and replacing it if you're strong in the
11:11
arm and weaken the head like me you can
11:13
sometimes snap the nut or the bolt with
11:16
lots of leverage
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but above 12 millimeter or half inch
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you'll need extremely long lever or very
11:23
strong arms
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so how can we avoid galling well the
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first thing is to slow down your
11:30
installation speed
11:31
don't use bolts to pull joints together
11:35
use a lubricant such as tef gel
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avoid damaged or dirty threads and use
11:41
extra care with lock nuts
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if a fastener binds or begins to bind
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you should stop immediately
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so while we're actually outside the
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chandler's here these guys are great
12:01
um
12:04
ozaturq marin
12:06
or east marine
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they're actually in our marina and
12:09
they're really good they've got all the
12:11
stuff he sells a lot of second-hand
12:13
stuff as well so you know when you want
12:15
the odd bits and pieces
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he's quite often got a secondhand one
12:19
but a couple of things that
12:22
i wanted to show you this is
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a hose clamp
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and this is a you know a quality german
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hose clamp
12:30
made
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it's actually stamped inside
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the stainless
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but look at this this is the bolt
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which tightens it up
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you can see that's just
12:44
mild still
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possibly coated
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there's a galvanized one
12:55
same thing and there's another one
13:02
so
13:02
again
13:05
this piece is stamped stainless steel
13:07
but the
13:09
the bolt that goes through the center
13:12
is just northern ordinary carbon steel
13:15
so when you buy hose clamps or jubilee
13:17
clamps make sure you take your magnet
13:19
with you and make sure that the securing
13:21
nut that tightens it up is not magnetic
13:25
and it's not carbon steel
13:27
the same thing applies when you're
13:29
buying fittings or fixtures
13:31
make sure you're getting what you're
13:33
actually paying for
13:34
and the same with some fixings now some
13:38
fixings can be very slightly magnetic
13:40
especially if they're an a4 80 grade
13:43
but talk to your supplier about this
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if they're reputable they won't mind you
13:49
asking questions
13:52
this is our local steel fabricator and
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he's very good
13:56
he never throws anything away because he
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knows the value of good quality
14:00
stainless steel and when you want to go
14:03
and have something made he's usually got
14:05
something there which will fit the bill
14:08
and may be able to be repurposed
14:11
everything that comes out of the
14:12
workshop is extremely well polished and
14:15
here he's making
14:17
some extension pieces for a fishing rod
14:19
holder for the frame we're about to look
14:22
at let's take a look at the welding on
14:24
this frame
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so this is what a good stainless steel
14:29
world should look like
14:31
they've been acid etched
14:32
and then have a high polish
14:34
these are really good worlds
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and this is the type of quality you
14:39
should be looking for if you're having
14:41
welding done
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or you're approaching someone to do
14:44
welding for you
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don't be afraid to ask for samples or to
14:49
see samples of their previous work
14:52
a good fabricator or engineering shop
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will only be too happy to show you the
14:57
type of quality that they can turn out
15:00
the difference in world quality is
15:03
pretty much self-explanatory what you
15:05
see is what you get on the left is a bad
15:09
world done with a mig welder and on the
15:11
right a good world with the tig welder
15:15
the difference pretty plain to see what
15:18
you see is what you get
15:22
metallogy is a really complicated
15:24
subject and there's lots more detail
15:26
that we could go into but not in this
15:28
video if you go to our website
15:31
and then scroll over to the technical
15:34
stuff you'll see that there's a pdf
15:36
version
15:37
of this video which you can reference or
15:40
use with your sailing club or just
15:42
general information
15:43
you can download it
15:45
for free along with lots of other bits
15:47
and bobs
15:48
pop over to svmpavidus.com
15:51
hopefully this video has been of use to
15:53
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15:54
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15:58
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