Bronze Brass ... Arrgh!

[eherlihy]

One of the nice features of my boat is that it had a Perko Strainer added by the PO. Unfortunately, now that I am in the midst of refitting her, I see that there was a lot of Mickey-mouse-ness...

The BRONZEthrough hull had a 5/8 BRASS barb screwed into it, and a 1˝" square wooden backing plate that had been coated with epoxy. It also had an external strainer. I tossed the through hull, and completed the installation (a-la Maine Sail) of a 3/4" through hull with a 3˝" backing block. The hose connector is now 3/4" BRONZE .

The Perko strainer has a BRONZE body and has threaded ˝" inlets and outlets, into which you can screw the appropriate barb fitting for the hose that you plan to use. Both connectors had ˝" to 5/8" BRASS connectors. These connectors should have been BRONZE to prevent weakening and leaks from galvanic corrosion. The connectors have been tossed, and are now in the trash.

The connection to the water pump was a ˝" BRASS barb that had the hose clamp tightened down to seal the 5/8" hose... The pump is also BRONZE.... I have since replaced this with ˝" hose, and should not have an issue finding a ˝" to ˝ Bronze tailpeice.

The problem is the strainer. I cannot find a 3/4 barb to ˝" male tailpiece. The guy at WM looked for 45 minutes, and couldn't find one either. Because the strainer is at the water line, I do not want to use a nylon tailpeice (which I can easily find).

My current thought is that I may have to either toss the entire strainer, and buy a new one with 3/4", or 1" connections ($$$), or somehow re-bore the existing strainer and make it 3/4".

Thoughts??? Help???

Thanks in advance!

[eherlihy]

HA! I found the solution:

Put this piece in the strainer inlet:

PIPE TO HOSE .50" PIPE X 3/4" HOSE 90 DEG FULL FLO BRZ

(the guy at WM couldn't find anything like this)

and one of these in the strainer outlet:

ADAPTER PIPE TO HOSE .50" STRAIGHT BRZ

this took me 15 min to find, once I started looking. The cost, including shipping, will be $30.

Lesson here: Just because the guy at WM can't find it, that does not mean that it doesn't exist.

[eherlihy]

For more information on my concern;

Silicon Bronze
Silicon bronze, often referred to simply as bronze, is an alloy made mostly of copper and tin with a small amount of silicon. Bronze is used primarily in marine environments. It is preferred over stainless in wooden boat construction and re-fastening due to its superior corrosion resistance, and over brass due to its higher strength. Bronze is similar to copper in color and is also sometimes seen in fine woodworking where it is used for its appearance. The main drawback of bronze is its high cost.

Brass
Brass is an alloy of primarily copper and zinc. Brass is highly corrosion resistant and electrically conductive. However, its use as a fastener is somewhat limited due to its relative softness. It is used primarily for its appearance.

- Bolt Depot

and

The difference between bronze and brass in the world of plumbing fittings concerns their relative potentials for galvanic corrosion. Dissimilar metals in contact can set up an electric current in an electrically conductive fluid (an electrolyte, such as saltwater). One of the metals will be "eaten away" or "sacrificed" in the process. Sacrificial anodes are made of zinc because it is one of the least "noble" (i.e., highly active) metals and is thus sacrificed to protect your engine, rudder, propeller shaft, refrigeration condenser, etc. from damage due to galvanic corrosion. However, with thru-hulls, seacocks, etc. dissolving fittings are not an option. You want all the fittings to remain intact.
To avoid this potentially hazardous situation, make sure you are not setting up the conditions for galvanic corrosion by connecting dissimilar brass fittings to bronze fittings. Generally, you can tell them apart just by looking at them. Bronze fittings have an outer surface that is rough in feel and appearance, almost like it's covered with sand. That's because bronze fittings are sand cast, and then machined.

So what should you do?
You should continue with what has always been sound marine practice: use bronze fittings for the thru-hull mushrooms, seacocks, strainer bodies and valves. If one of the pipes must be turned through an angle, use a bronze Street Ell, either 90° or 45°. Once the bronze fittings are in place and aligned, thread a bronze hose barb into each, and join them with sturdy hoses and stainless steel clamps.
Don't confuse bronze hose-to-pipe fittings like those made by Groco and Perko with small brass hose-to-pipe adapters. Bronze fittings used for seacocks are fine for use in saltwater.

- West Marine

[Maine Sail]

Compound onto all that the fact that most seacocks, thru-hulls and true bronze fittings for below water are 85-5-5-5 bronze and most all struts and props are Manganese Bronze which is really more like 38-39% ZINC and you can have a real galvanic soup if you're not well protected.

85-5-5-5 is not strong enough for struts or props so Manganese Bronze (really more like a brass) or Nibral are used. Nibral is very expensive so most builders opt for the high zinc Manganese bronze for props, struts, gudgeon's, rudder shoes or sand shoes.

In Europe they use what they refer to as DRZ-1 which is also a very high zinc content "bronze" with a tad but of tin added to try and increase its resistance to dezincification. Personally I won't touch DRZ-1 for seacock fittings as I have seen too many European boats with dezincification far to early.. On the other hand I have seen some 40+ year old 85-5-5-5 bronze seacocks that still look like new. Got an old tapered cone on my bench right now that is over 40 years old and ready for another 40 after some lapping and new grease..

If you think all your mismatched metals are bad take the paint off a Universal/Westerbeke HX!!!

This is why they MUST have a zinc..