Re: Re: [CR]Re: (was silca) now Chromed Plastic


From: "Aldo Ross" <swampmtn@siscom.net>
To: <classicrendezvous@bikelist.org>
References: <b5.76def21.27c6adc4@aol.com>
Subject: Re: Re: [CR]Re: (was silca) now Chromed Plastic
Date: Thu, 22 Feb 2001 13:26:12 -0500


(from http://www.bergen.org)

Metals Plating Plastics Plating can be successfully performed on many plastics, including ABS, polypropylene, polysulfone, modified poly-phenylene oxide, polycarbonate, polyester, and nylon, to provide a decorative finish or a hard surface for wear and corrosion resistance. Plating can improve physical properties of the plastics part, such as tensile and flexural strength and the heat deflection temperature. Because of their light weight and Nickel ease of design, plastics have been used in many applications to replace zinc die castings, brass, and steel. The total cost to plate plastics is competitive with metals. Because of their light weight and ease of design, plastics have been used in many applications replace zinc die castings, brass, and steel. The total cost to plate to plastics is competitive with metals. Product design of parts to be plated is particularly critical in determining the success of the plating operation. Basic plastics design practices should be followed to achieve a good molding in the unplated product, and it is advisable to have the design reviewed by the plater. Because the proper choice of resin for products to be plated is of basic importance, the resin supplier should be consulted while the product is in the design stage. Preplate Cycle Since plastics are nonconductive. they must first be processed through a preplate cycle, during which a metallic coating is deposited by an electroless plating process to make the plastics part conductive. The preplate cycle consists of etching, neutralizing, catalyzing, acceleration, and electroless plating.

Etching The etch bath consists of a highly concentrated acid solution of chromic and sulfuric acid. The solution oxidizes selective aresas on the plastics part. The holes produced by the oxidizing action are absorbing sites that hold small metallic particles that serve as acitvators for electroless plating. The hole size influences adhesion and other physical properties. After etching, the plastic is throughly rinsed.

Neutralizing (sensitizing) The neutralizing bath containing mild acids or alkaline solutions chemically neutralize the acids from the etching bath.

Catalyzing In this step, a catalytic film is put on the oxidized surface to prepare for electroless meatl disposition. It is done in two steps, in step 1 the liquid is immersed in a bath, step 2 involves another solution that prepare the plastic to be plated by nickel.

Acceleration The accelerator bath remove all the chemical that remain after the Catalyzing procedure. It also accelerates the catalyzic film, to ensure a rapid coverage of electroless deposits.

Electroless Plating The plating bath is the final bath of the preplate cycle. A thin deposit of metallic file is deposited on the plastics part. It can be made of nickel or copper depending on the objects application. Electroless plating helps electroplated plastics in a corrsosive environment.

What we have done We are doing the above following step in our rapidprototyping project. We are eletroless plating Nickel to plastic which are steps 1-5. The steps below are intended for informational purposes only.

Plating There are many kind of ways to plate plastics. Some of the following are:

Strike bath Acid copper bath Semibright nickel bath Chromium plating bath Solution Control The process descibed above should be done in the best of conditions possible. You should rinse the object being plated after every step taken. There should be careful watch over different aspects of each constituent. pH levels, temperature, or brightener level flucutations may ruin the whole process. The Hull cell is one of the most vital tools in electroplating. It can show current ranges, the apperance of the deposit, and check if there are impurities. If there are any changes in the solution the Hull cell would know. Troubleshooting electroplating is a long and lengthy process. There are hundreds and hundreds of possible explanations for why your bath is bad. You should be able to know the most common troubleshooting tips if you were to start electroplating for industry.

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(from http://www.bergen.org) Aldo Ross