This paper describes the environment impact of low-lime calcium silicate (Ca2SiO4) cement (CSC) that cures by a reaction with gaseous carbon dioxide (CO2). The production of CSC requires less limestone and lower kiln temperatures than those used for ordinary Portland cement (OPC). This makes it possible to reduce the carbon dioxide emissions at the cement kiln from ∼810 kg/t for OPC to ∼565 kg/t for CSC. The carbon dioxide used in the curing process and captured within CSC-based concrete (CSC-C) is industrial-grade carbon dioxide sourced from waste flue gas streams. The fully hardened CSC-C will contain up to 300 kg of carbon dioxide per tonne of cement used in the concrete formulation. This paper also summarises the performance and durability of CSC-C and OPC concrete (OPC-C). Freeze–thaw and scaling resistance were evaluated as per ASTM C666 and ASTM C672, respectively, the concentrations of ionic species leached from the concretes were measured, efflorescence was evaluated in pavers partially submerged in water, and the expansion and mass changes associated with the exposure to sodium sulfate (Na2SO4) and magnesium (Mg) solutions were measured. In each of the durability tests, the CSC-C specimens, made with commercially produced Solidia Cement, performed equivalently or better than the OPC-C specimens.

Chromates are widely used as corrosion inhibitors and are effective both in solvent-based and waterborne metal primers. Zinc phosphate is a conventional corrosion inhibitor but is not found to be a good inhibitor in the conventional primers. However, in our study zinc phosphate has been found to be a very effective inhibitor in the silane-based waterborne primers. The study began with screening from a wide variety of inhibitors. Zinc phosphate (ZP) was found to be an overall best pigment for our superprimers, a series of one-step, low-VOC, and chromate-free waterborne primers. Epoxy/acrylate-based superprimer containing similar to 20 wt% ZP performed well on aluminum and steel alloys and novolac epoxy-based superprimer containing similar to 15 wt% ZP works well specifically on aluminum alloys.The protection mechanism of zinc phosphate in the two superprimers is studied. SEM/EDS study shows epoxy/acrylate-based superprimer was found to have a stratified double layer structure, with a less-penetrable hydrophobic layer on the top and a hydrophilic layer accommodating the inhibitors underneath, while novolac epoxy-based superprimer shows a relatively uniform structure. The presence of silane was found to be critical for the adhesion and anticorrosion performance of the primer.

With the use of silane-containing primer technology the chromate in the conversion coating and the primer as well as the volatile organic compounds of the primer can be eliminated. This primer, which is based on water-dispersed resins, crosslinkers and silanes, is applied onto the substrate directly after alkaline cleaning. Because of the organofunctional silane contained in the primer, its adhesion to the substrate is maintained even without a pretreatment layer. The corrosion resistance of the primer is assured by incorporating chromate-free corrosion-inhibiting pigments into the formulation. For industrial applications, primers need to be dividable into packs and should be compatible for many different coating systems. This paper reports on two phases of investigation of an epoxy-acrylate primer. In the first phase this primer is divided into packs and its performance and chemistry are studied in an aircraft coating system. In the second phase the same primer and its improved version are studied in an automotive coating system and are compared with an automotive reference coating system. Our study reveals that the primer is dividable into packs and the performance of the primer is promising in both applications.

In previous research we have demonstrated that the commonly used pretreatment for automotive steels via zinc phosphating, can be replaced by simple treatments with solutions of organofunctional silanes without loss of performance in the standard corrosion tests. Now we report on a new development in which we have replaced both the phosphating step and the cathodic electrocoat system with one primer system. This particular primer is based on an epoxy-acrylate binder, organofunctional silane, crosslinker and anti-corrosion pigment. This primer can be denoted as a 2-in-1 primer, as no conversion coating is required. Bonding to the substrate is affected by the silane in the primer. Two versions of this primer were tested in an automotive coating system in different performance tests on electrogalvanized (EZG) steel, hot-dip galvanized (HDG) steel and on cold-rolled steel (CRS). The reference panels contained the same automotive coating on zinc phosphated and e-coated substrates. The initial results are reported here. All panels had excellent dry and wet tape paint adhesion. The salt water immersion and salt spray test results of the test panels were comparable with those of the reference panels. In the Ford APGE test, the new primer substrates tended to form more white rust in the scribe than the reference samples, which formed more red rust. A tentative mechanism for the high performance of the 2-in-1 primer will be presented.

Coatings derived from organofunctional silanes have been investigated as possible replacements for the chromate-based systems used in the aerospace industry. In this study, organofunctional silanes [bis-(triethoxysilylpropyl)ethane and bis(triethoxysilylpropyl) tetrasulfide] were reacted with commercially available acrylate (ECO-CRYL (TM) 9790) and epoxy (EPI-REZ (TM) WD-510) resins, resulting in a one-step, low-VOC, chromate-free primer. Liquid-state Si-29 and C-13 NMR were used to determine structural characteristics of various optimized formulations.Once the components of a multi-component primer are mixed to formulate a solution the chemical reactions start between the various components. The primer solution is required to provide enough time before significant changes have occurred so as to facilitate a comfortable window for application on the substrates desired. The liquid-state NMR studies were conducted to investigate the pot-life chemistry of the primer solution after the components have been mixed. Described here are the possible chemical reactions occurring in the liquid primer solution. The reactions during curing of the coating have been investigated with SEM/EDX and FTIR and have been reported elsewhere. (c) 2007 Elsevier B.V. All rights reserved.

In this paper, we have used a Taguchi method approach for the optimization of 5 different novel room-temperature cured primers. These novel primers were developed for the replacement of the chromate-based Cr(VI) technology currently used for the corrosion protection of aerospace alloys such as AA 2024-T3. However, Cr(VI) has been identified by the Environmental Protection Agency (EPA) as toxic and carcinogenic and a replacement for it is being sought. The 5 systems differ in the type of organofunctional silane used for formulating the primer. The five different organofunctional silanes used were bis-(triethoxysilylpropyl) ethane (BTSEsilane), bis-(triethylsilylpropyl) tetrasulfide (bis-sulfur silane), and combinations of the above silanes in the weight ratios 1:2, 2:1 and 1:1 respectively. The components of the room temperature primer were acrylate resin, an epoxy resin, one of the five organofunctional silane system and a crosslinker. An L9 orthogonal array was chosen with the parameters set as the components of the primer. The levels were varied through three different amounts for the resins and the silane or silane combinations. The crosslinker amount was fixed and was varied by using three different types of crosslinker. Various corrosion performance tests were conducted on the samples coated with the primers formulated. Electrochemical Impedance spectroscopy (EIS), 3.5 wt-% NaCl aqueous solution immersion test, DI water contact angle before and after exposure to 3.5 wt-% NaCl aqueous solution, tape adhesion test (ASTM D 3359), MEK double rub test (ASTM D 4752), chemical resistance test (ASTM D 3912) were used as performance evaluation tests. Using the results obtained from these experiments an optimized formulation was obtained for primers formulated with each of the five different primer systems.

: The concept of superprimers, i.e., primers for metals with the conversion coating built in, has proven to be feasible. Such primers can be applied on any bare metal, provided it is reasonably clean. These primers are based on water-dispersed organic resins and organofunctional silanes, which assure good adhesion both to the substrate and the overcoat. In this paper we will discuss an epoxy-novolac based system for AA20242-T3, but we will also present an overview of other coatings. The corrosion protection performance of these coatings has been evaluated using electrochemical methods and performance tests. All of the developed coatings survive 2000 hrs in ASTM B117 salt spray test. The systems have also been extensively characterized. The characterization methods have provided information on the formation of the coatings and the mechanism by which the coatings protect the metal substrates.