Bronze Screws

[bruceS]

I plan on starting to build an Ocean Pointer in a week or two and just received a shipment of silicon bronze screws, nails, etc. The vast majority of pieces share the same dirty reddish color of silicon bronze, but certain sizes of screws, washers and nuts either have a distinctive copper color or a brass color. The small and large washer look like pure copper which may not be a concern, but the nuts and two of the screw sizes look like they are not naval bronze.

The supplier assures me that everything is naval bronze and the questionable parts may have come from a different supplier.

I have attached an image which does not give justice to the very brassy look of two of the screws and the nuts.

Should I be concerned? http://www.brine.ca/graphics/bronze.jpg

The Ocean Pointer design has been altered to allow installation of a 33 HP 4 cylinder diesel amidship.

[ 01-13-2004, 05:42 PM: Message edited by: bruceS ]

[gary porter]

Bruce, Silicon Bronze does vary with whoever makes it in its alloy content and Naval Bronze and Silicon Bronze may well have different meanings to different manufacturers.
Most of the Silicon Bronze hardware is now imported and thus the variance.
Your first and third screw and the bolt look like legitimate silicon bronze to me. The second screw and definately the large screw look like naval brass. The washers look like just copper washers. Just my opinion of course and if it were me I'd find another supplier.
Gary

[The Gentleman Sawyer]

Excellent Photo!

The Gentleman Sawyer

[Ross M]

I have posted this test before, but I cannot locate it in the archives. This is taken directly from ASTM STP550, which was developed by Langley Research Center (NASA).

First Separate by Color:

Reddish or red brown color: Coppers, Berylco 50, Berylco 10
Dark yellow color: Bronzes, beryllium copper, red brass
Light yellow: Brasses, silver solder, manganese bronze

For Dark Yellow Colors:

2 Drops concentrated Nitric Acid (sp gr 1.42)
After 2 minutes add 2 drops water
White precipitate: Tin bronze, high leaded tin bronze, phosphor bronze;
Oily drop with white precipitate: Silicon bronze, oil impregnated bronze
No precipitate: Beryllium copper, aluminum bronze, red brass

If white precipitate:

1 drop ferric chloride, observe after 1 minute
Black spot: Phosphor bronze
No black spot: Tin bronze, high leaded tin bronze

For Light Yellow Colors:

3 drops concentrated nitric acid on surface, after 2 minutes transfer 1 drop to porcelain spot plate and add 1 drop sodium bismuthate solution (3.5 grams sodium bismuthate mixed with 60 milliliters of water)
Purple color: Manganese bronze
Black color: Silver solder (requires further confirmation tests)
Brown color: Brasses - QQ-B-626B, QQ-B-613B, yellow, admiralty, naval or aluminum

Hope you find this helpful!

Ross

Edited to add: I do not believe that there is a metal called "Naval Bronze". Both this test and Mark's Handbook refer only to Naval Brasses, which contain 37-39% zinc...

[ 01-13-2004, 09:07 PM: Message edited by: Ross McDonough ]

[bruceS]

Thank-you Ross!

I'll give it a try.

Bruce S,
Parksville, canada

[RonW]

Very good picture. I would like to know the supplier. I agree with gary porter, the first and third screw looks o.k. but a little coppery, and the bolt looks dead on silicon bronze, the rest appears to be junk. Do a search on this board for bronze, just a couple pages back is a lot of discussion about suppliers buying cheaper stuff from asia.And I will say it, when suppliers buy cheaper stuff and sell it for the same price as the good stuff- It is called ripping off.In your search you should also find where a gentlemen from approximately last summer was asking where he could get silicon bronze tested. As i remember his silicon bronze screws where detearorating in his boat after only six years.I find it dissheartening to spend the time,and money to build a boat, and then find out the premium materials you paid for, you didn't get.

[John E Hardiman]

If it's not just "brass" it should be marked. Look for a 3 digit code like the "651" and "687"(?) as shown on the washer and the nut and most likely on the bolthead (screws may not have any or just dots). Then find a metals handbook or do a web search for "copper alloy cXXX". All enhanced copper products are "supposed" to be marked by federal code to prevent brass from being inserted. The Navy lost some people a few years ago when brass was used to replace bronze in a steam system on one of the LHAs overseas. But we still get some vendors that try to pass off stuff that is either not marked of is "incorrectly" marked.

[bruceS]

UPDATE:
I have not done the acid test as I am unable to find the necessary ingredients. I took all the pieces to a local foundry, who agreed that two screw sizes were suspicious. I talked with a local competitor who spoke very highly of the place where I purchased the parts.
The 651 number on the large washer is the code for silicon bronze. The 561 stamp on the nuts makes no sense, but they have all been stamped twice. I cannot read the first number stamped, but it could very well be 561 (confusion in the Taiwan factory? :)).

[whb]

If you read the washer straight across it reads 561. I wonder if an overseas factory merely read it this way and stamped it on their nuts (that must have hurt) without regard to the meaning.

Howard

[John E Hardiman]

Originally posted by whb:
If you read the washer straight across it reads 561. I wonder if an overseas factory merely read it this way and stamped it on their nuts (that must have hurt) without regard to the meaning.

HowardThere is a code standard; I'd have to dig it out. Mil-Specs sell out how it will be marked, but we've been "mainstreamed" and civil codes are much more lax. At one time it was estimated that 50% of the bolts sold in the US had forged, as in purposefully incorrect, headmarkings.

[ 01-14-2004, 05:55 PM: Message edited by: John E Hardiman ]

[Big Red]

If they are suspect, why not take them back to the supplier and replace them with stainless? :confused: